/* * FUSE: Filesystem in Userspace * Copyright (C) 2001-2007 Miklos Szeredi * * This program can be distributed under the terms of the GNU GPLv2. * See the file COPYING. */ /* * * This file system mirrors the existing file system hierarchy of the * system, starting at the root file system. This is implemented by * just "passing through" all requests to the corresponding user-space * libc functions. In contrast to passthrough.c and passthrough_fh.c, * this implementation uses the low-level API. Its performance should * be the least bad among the three, but many operations are not * implemented. In particular, it is not possible to remove files (or * directories) because the code necessary to defer actual removal * until the file is not opened anymore would make the example much * more complicated. * * When writeback caching is enabled (-o writeback mount option), it * is only possible to write to files for which the mounting user has * read permissions. This is because the writeback cache requires the * kernel to be able to issue read requests for all files (which the * passthrough filesystem cannot satisfy if it can't read the file in * the underlying filesystem). * * Compile with: * * gcc -Wall passthrough_ll.c `pkg-config fuse3 --cflags --libs` -o * passthrough_ll * * ## Source code ## * \include passthrough_ll.c */ #include "qemu/osdep.h" #include "qemu/timer.h" #include "fuse_virtio.h" #include "fuse_log.h" #include "fuse_lowlevel.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "passthrough_helpers.h" #include "passthrough_seccomp.h" /* Keep track of inode posix locks for each owner. */ struct lo_inode_plock { uint64_t lock_owner; int fd; /* fd for OFD locks */ }; struct lo_map_elem { union { struct lo_inode *inode; struct lo_dirp *dirp; int fd; ssize_t freelist; }; bool in_use; }; /* Maps FUSE fh or ino values to internal objects */ struct lo_map { struct lo_map_elem *elems; size_t nelems; ssize_t freelist; }; struct lo_key { ino_t ino; dev_t dev; }; struct lo_inode { int fd; /* * Atomic reference count for this object. The nlookup field holds a * reference and release it when nlookup reaches 0. */ gint refcount; struct lo_key key; /* * This counter keeps the inode alive during the FUSE session. * Incremented when the FUSE inode number is sent in a reply * (FUSE_LOOKUP, FUSE_READDIRPLUS, etc). Decremented when an inode is * released by requests like FUSE_FORGET, FUSE_RMDIR, FUSE_RENAME, etc. * * Note that this value is untrusted because the client can manipulate * it arbitrarily using FUSE_FORGET requests. * * Protected by lo->mutex. */ uint64_t nlookup; fuse_ino_t fuse_ino; pthread_mutex_t plock_mutex; GHashTable *posix_locks; /* protected by lo_inode->plock_mutex */ mode_t filetype; }; struct lo_cred { uid_t euid; gid_t egid; }; enum { CACHE_NONE, CACHE_AUTO, CACHE_ALWAYS, }; struct lo_data { pthread_mutex_t mutex; int debug; int writeback; int flock; int posix_lock; int xattr; char *source; char *modcaps; double timeout; int cache; int timeout_set; int readdirplus_set; int readdirplus_clear; int allow_direct_io; struct lo_inode root; GHashTable *inodes; /* protected by lo->mutex */ struct lo_map ino_map; /* protected by lo->mutex */ struct lo_map dirp_map; /* protected by lo->mutex */ struct lo_map fd_map; /* protected by lo->mutex */ /* An O_PATH file descriptor to /proc/self/fd/ */ int proc_self_fd; }; static const struct fuse_opt lo_opts[] = { { "writeback", offsetof(struct lo_data, writeback), 1 }, { "no_writeback", offsetof(struct lo_data, writeback), 0 }, { "source=%s", offsetof(struct lo_data, source), 0 }, { "flock", offsetof(struct lo_data, flock), 1 }, { "no_flock", offsetof(struct lo_data, flock), 0 }, { "posix_lock", offsetof(struct lo_data, posix_lock), 1 }, { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 }, { "xattr", offsetof(struct lo_data, xattr), 1 }, { "no_xattr", offsetof(struct lo_data, xattr), 0 }, { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 }, { "timeout=%lf", offsetof(struct lo_data, timeout), 0 }, { "timeout=", offsetof(struct lo_data, timeout_set), 1 }, { "cache=none", offsetof(struct lo_data, cache), CACHE_NONE }, { "cache=auto", offsetof(struct lo_data, cache), CACHE_AUTO }, { "cache=always", offsetof(struct lo_data, cache), CACHE_ALWAYS }, { "readdirplus", offsetof(struct lo_data, readdirplus_set), 1 }, { "no_readdirplus", offsetof(struct lo_data, readdirplus_clear), 1 }, { "allow_direct_io", offsetof(struct lo_data, allow_direct_io), 1 }, { "no_allow_direct_io", offsetof(struct lo_data, allow_direct_io), 0 }, FUSE_OPT_END }; static bool use_syslog = false; static int current_log_level; static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode, uint64_t n); static struct { pthread_mutex_t mutex; void *saved; } cap; /* That we loaded cap-ng in the current thread from the saved */ static __thread bool cap_loaded = 0; static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st); static int is_dot_or_dotdot(const char *name) { return name[0] == '.' && (name[1] == '\0' || (name[1] == '.' && name[2] == '\0')); } /* Is `path` a single path component that is not "." or ".."? */ static int is_safe_path_component(const char *path) { if (strchr(path, '/')) { return 0; } return !is_dot_or_dotdot(path); } static struct lo_data *lo_data(fuse_req_t req) { return (struct lo_data *)fuse_req_userdata(req); } /* * Load capng's state from our saved state if the current thread * hadn't previously been loaded. * returns 0 on success */ static int load_capng(void) { if (!cap_loaded) { pthread_mutex_lock(&cap.mutex); capng_restore_state(&cap.saved); /* * restore_state free's the saved copy * so make another. */ cap.saved = capng_save_state(); if (!cap.saved) { pthread_mutex_unlock(&cap.mutex); fuse_log(FUSE_LOG_ERR, "capng_save_state (thread)\n"); return -EINVAL; } pthread_mutex_unlock(&cap.mutex); /* * We want to use the loaded state for our pid, * not the original */ capng_setpid(syscall(SYS_gettid)); cap_loaded = true; } return 0; } /* * Helpers for dropping and regaining effective capabilities. Returns 0 * on success, error otherwise */ static int drop_effective_cap(const char *cap_name, bool *cap_dropped) { int cap, ret; cap = capng_name_to_capability(cap_name); if (cap < 0) { ret = errno; fuse_log(FUSE_LOG_ERR, "capng_name_to_capability(%s) failed:%s\n", cap_name, strerror(errno)); goto out; } if (load_capng()) { ret = errno; fuse_log(FUSE_LOG_ERR, "load_capng() failed\n"); goto out; } /* We dont have this capability in effective set already. */ if (!capng_have_capability(CAPNG_EFFECTIVE, cap)) { ret = 0; goto out; } if (capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, cap)) { ret = errno; fuse_log(FUSE_LOG_ERR, "capng_update(DROP,) failed\n"); goto out; } if (capng_apply(CAPNG_SELECT_CAPS)) { ret = errno; fuse_log(FUSE_LOG_ERR, "drop:capng_apply() failed\n"); goto out; } ret = 0; if (cap_dropped) { *cap_dropped = true; } out: return ret; } static int gain_effective_cap(const char *cap_name) { int cap; int ret = 0; cap = capng_name_to_capability(cap_name); if (cap < 0) { ret = errno; fuse_log(FUSE_LOG_ERR, "capng_name_to_capability(%s) failed:%s\n", cap_name, strerror(errno)); goto out; } if (load_capng()) { ret = errno; fuse_log(FUSE_LOG_ERR, "load_capng() failed\n"); goto out; } if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, cap)) { ret = errno; fuse_log(FUSE_LOG_ERR, "capng_update(ADD,) failed\n"); goto out; } if (capng_apply(CAPNG_SELECT_CAPS)) { ret = errno; fuse_log(FUSE_LOG_ERR, "gain:capng_apply() failed\n"); goto out; } ret = 0; out: return ret; } static void lo_map_init(struct lo_map *map) { map->elems = NULL; map->nelems = 0; map->freelist = -1; } static void lo_map_destroy(struct lo_map *map) { free(map->elems); } static int lo_map_grow(struct lo_map *map, size_t new_nelems) { struct lo_map_elem *new_elems; size_t i; if (new_nelems <= map->nelems) { return 1; } new_elems = realloc(map->elems, sizeof(map->elems[0]) * new_nelems); if (!new_elems) { return 0; } for (i = map->nelems; i < new_nelems; i++) { new_elems[i].freelist = i + 1; new_elems[i].in_use = false; } new_elems[new_nelems - 1].freelist = -1; map->elems = new_elems; map->freelist = map->nelems; map->nelems = new_nelems; return 1; } static struct lo_map_elem *lo_map_alloc_elem(struct lo_map *map) { struct lo_map_elem *elem; if (map->freelist == -1 && !lo_map_grow(map, map->nelems + 256)) { return NULL; } elem = &map->elems[map->freelist]; map->freelist = elem->freelist; elem->in_use = true; return elem; } static struct lo_map_elem *lo_map_reserve(struct lo_map *map, size_t key) { ssize_t *prev; if (!lo_map_grow(map, key + 1)) { return NULL; } for (prev = &map->freelist; *prev != -1; prev = &map->elems[*prev].freelist) { if (*prev == key) { struct lo_map_elem *elem = &map->elems[key]; *prev = elem->freelist; elem->in_use = true; return elem; } } return NULL; } static struct lo_map_elem *lo_map_get(struct lo_map *map, size_t key) { if (key >= map->nelems) { return NULL; } if (!map->elems[key].in_use) { return NULL; } return &map->elems[key]; } static void lo_map_remove(struct lo_map *map, size_t key) { struct lo_map_elem *elem; if (key >= map->nelems) { return; } elem = &map->elems[key]; if (!elem->in_use) { return; } elem->in_use = false; elem->freelist = map->freelist; map->freelist = key; } /* Assumes lo->mutex is held */ static ssize_t lo_add_fd_mapping(fuse_req_t req, int fd) { struct lo_map_elem *elem; elem = lo_map_alloc_elem(&lo_data(req)->fd_map); if (!elem) { return -1; } elem->fd = fd; return elem - lo_data(req)->fd_map.elems; } /* Assumes lo->mutex is held */ static ssize_t lo_add_dirp_mapping(fuse_req_t req, struct lo_dirp *dirp) { struct lo_map_elem *elem; elem = lo_map_alloc_elem(&lo_data(req)->dirp_map); if (!elem) { return -1; } elem->dirp = dirp; return elem - lo_data(req)->dirp_map.elems; } /* Assumes lo->mutex is held */ static ssize_t lo_add_inode_mapping(fuse_req_t req, struct lo_inode *inode) { struct lo_map_elem *elem; elem = lo_map_alloc_elem(&lo_data(req)->ino_map); if (!elem) { return -1; } elem->inode = inode; return elem - lo_data(req)->ino_map.elems; } static void lo_inode_put(struct lo_data *lo, struct lo_inode **inodep) { struct lo_inode *inode = *inodep; if (!inode) { return; } *inodep = NULL; if (g_atomic_int_dec_and_test(&inode->refcount)) { close(inode->fd); free(inode); } } /* Caller must release refcount using lo_inode_put() */ static struct lo_inode *lo_inode(fuse_req_t req, fuse_ino_t ino) { struct lo_data *lo = lo_data(req); struct lo_map_elem *elem; pthread_mutex_lock(&lo->mutex); elem = lo_map_get(&lo->ino_map, ino); if (elem) { g_atomic_int_inc(&elem->inode->refcount); } pthread_mutex_unlock(&lo->mutex); if (!elem) { return NULL; } return elem->inode; } /* * TODO Remove this helper and force callers to hold an inode refcount until * they are done with the fd. This will be done in a later patch to make * review easier. */ static int lo_fd(fuse_req_t req, fuse_ino_t ino) { struct lo_inode *inode = lo_inode(req, ino); int fd; if (!inode) { return -1; } fd = inode->fd; lo_inode_put(lo_data(req), &inode); return fd; } static void lo_init(void *userdata, struct fuse_conn_info *conn) { struct lo_data *lo = (struct lo_data *)userdata; if (conn->capable & FUSE_CAP_EXPORT_SUPPORT) { conn->want |= FUSE_CAP_EXPORT_SUPPORT; } if (lo->writeback && conn->capable & FUSE_CAP_WRITEBACK_CACHE) { fuse_log(FUSE_LOG_DEBUG, "lo_init: activating writeback\n"); conn->want |= FUSE_CAP_WRITEBACK_CACHE; } if (conn->capable & FUSE_CAP_FLOCK_LOCKS) { if (lo->flock) { fuse_log(FUSE_LOG_DEBUG, "lo_init: activating flock locks\n"); conn->want |= FUSE_CAP_FLOCK_LOCKS; } else { fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling flock locks\n"); conn->want &= ~FUSE_CAP_FLOCK_LOCKS; } } if (conn->capable & FUSE_CAP_POSIX_LOCKS) { if (lo->posix_lock) { fuse_log(FUSE_LOG_DEBUG, "lo_init: activating posix locks\n"); conn->want |= FUSE_CAP_POSIX_LOCKS; } else { fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling posix locks\n"); conn->want &= ~FUSE_CAP_POSIX_LOCKS; } } if ((lo->cache == CACHE_NONE && !lo->readdirplus_set) || lo->readdirplus_clear) { fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling readdirplus\n"); conn->want &= ~FUSE_CAP_READDIRPLUS; } } static void lo_getattr(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) { int res; struct stat buf; struct lo_data *lo = lo_data(req); (void)fi; res = fstatat(lo_fd(req, ino), "", &buf, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW); if (res == -1) { return (void)fuse_reply_err(req, errno); } fuse_reply_attr(req, &buf, lo->timeout); } static int lo_fi_fd(fuse_req_t req, struct fuse_file_info *fi) { struct lo_data *lo = lo_data(req); struct lo_map_elem *elem; pthread_mutex_lock(&lo->mutex); elem = lo_map_get(&lo->fd_map, fi->fh); pthread_mutex_unlock(&lo->mutex); if (!elem) { return -1; } return elem->fd; } static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr, int valid, struct fuse_file_info *fi) { int saverr; char procname[64]; struct lo_data *lo = lo_data(req); struct lo_inode *inode; int ifd; int res; int fd; inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); return; } ifd = inode->fd; /* If fi->fh is invalid we'll report EBADF later */ if (fi) { fd = lo_fi_fd(req, fi); } if (valid & FUSE_SET_ATTR_MODE) { if (fi) { res = fchmod(fd, attr->st_mode); } else { sprintf(procname, "%i", ifd); res = fchmodat(lo->proc_self_fd, procname, attr->st_mode, 0); } if (res == -1) { goto out_err; } } if (valid & (FUSE_SET_ATTR_UID | FUSE_SET_ATTR_GID)) { uid_t uid = (valid & FUSE_SET_ATTR_UID) ? attr->st_uid : (uid_t)-1; gid_t gid = (valid & FUSE_SET_ATTR_GID) ? attr->st_gid : (gid_t)-1; res = fchownat(ifd, "", uid, gid, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW); if (res == -1) { goto out_err; } } if (valid & FUSE_SET_ATTR_SIZE) { int truncfd; if (fi) { truncfd = fd; } else { sprintf(procname, "%i", ifd); truncfd = openat(lo->proc_self_fd, procname, O_RDWR); if (truncfd < 0) { goto out_err; } } res = ftruncate(truncfd, attr->st_size); if (!fi) { saverr = errno; close(truncfd); errno = saverr; } if (res == -1) { goto out_err; } } if (valid & (FUSE_SET_ATTR_ATIME | FUSE_SET_ATTR_MTIME)) { struct timespec tv[2]; tv[0].tv_sec = 0; tv[1].tv_sec = 0; tv[0].tv_nsec = UTIME_OMIT; tv[1].tv_nsec = UTIME_OMIT; if (valid & FUSE_SET_ATTR_ATIME_NOW) { tv[0].tv_nsec = UTIME_NOW; } else if (valid & FUSE_SET_ATTR_ATIME) { tv[0] = attr->st_atim; } if (valid & FUSE_SET_ATTR_MTIME_NOW) { tv[1].tv_nsec = UTIME_NOW; } else if (valid & FUSE_SET_ATTR_MTIME) { tv[1] = attr->st_mtim; } if (fi) { res = futimens(fd, tv); } else { sprintf(procname, "%i", inode->fd); res = utimensat(lo->proc_self_fd, procname, tv, 0); } if (res == -1) { goto out_err; } } lo_inode_put(lo, &inode); return lo_getattr(req, ino, fi); out_err: saverr = errno; lo_inode_put(lo, &inode); fuse_reply_err(req, saverr); } static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st) { struct lo_inode *p; struct lo_key key = { .ino = st->st_ino, .dev = st->st_dev, }; pthread_mutex_lock(&lo->mutex); p = g_hash_table_lookup(lo->inodes, &key); if (p) { assert(p->nlookup > 0); p->nlookup++; g_atomic_int_inc(&p->refcount); } pthread_mutex_unlock(&lo->mutex); return p; } /* value_destroy_func for posix_locks GHashTable */ static void posix_locks_value_destroy(gpointer data) { struct lo_inode_plock *plock = data; /* * We had used open() for locks and had only one fd. So * closing this fd should release all OFD locks. */ close(plock->fd); free(plock); } /* * Increments nlookup and caller must release refcount using * lo_inode_put(&parent). */ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name, struct fuse_entry_param *e) { int newfd; int res; int saverr; struct lo_data *lo = lo_data(req); struct lo_inode *inode = NULL; struct lo_inode *dir = lo_inode(req, parent); /* * name_to_handle_at() and open_by_handle_at() can reach here with fuse * mount point in guest, but we don't have its inode info in the * ino_map. */ if (!dir) { return ENOENT; } memset(e, 0, sizeof(*e)); e->attr_timeout = lo->timeout; e->entry_timeout = lo->timeout; /* Do not allow escaping root directory */ if (dir == &lo->root && strcmp(name, "..") == 0) { name = "."; } newfd = openat(dir->fd, name, O_PATH | O_NOFOLLOW); if (newfd == -1) { goto out_err; } res = fstatat(newfd, "", &e->attr, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW); if (res == -1) { goto out_err; } inode = lo_find(lo, &e->attr); if (inode) { close(newfd); } else { inode = calloc(1, sizeof(struct lo_inode)); if (!inode) { goto out_err; } /* cache only filetype */ inode->filetype = (e->attr.st_mode & S_IFMT); /* * One for the caller and one for nlookup (released in * unref_inode_lolocked()) */ g_atomic_int_set(&inode->refcount, 2); inode->nlookup = 1; inode->fd = newfd; inode->key.ino = e->attr.st_ino; inode->key.dev = e->attr.st_dev; pthread_mutex_init(&inode->plock_mutex, NULL); inode->posix_locks = g_hash_table_new_full( g_direct_hash, g_direct_equal, NULL, posix_locks_value_destroy); pthread_mutex_lock(&lo->mutex); inode->fuse_ino = lo_add_inode_mapping(req, inode); g_hash_table_insert(lo->inodes, &inode->key, inode); pthread_mutex_unlock(&lo->mutex); } e->ino = inode->fuse_ino; lo_inode_put(lo, &inode); lo_inode_put(lo, &dir); fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long long)parent, name, (unsigned long long)e->ino); return 0; out_err: saverr = errno; if (newfd != -1) { close(newfd); } lo_inode_put(lo, &inode); lo_inode_put(lo, &dir); return saverr; } static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name) { struct fuse_entry_param e; int err; fuse_log(FUSE_LOG_DEBUG, "lo_lookup(parent=%" PRIu64 ", name=%s)\n", parent, name); /* * Don't use is_safe_path_component(), allow "." and ".." for NFS export * support. */ if (strchr(name, '/')) { fuse_reply_err(req, EINVAL); return; } err = lo_do_lookup(req, parent, name, &e); if (err) { fuse_reply_err(req, err); } else { fuse_reply_entry(req, &e); } } /* * On some archs, setres*id is limited to 2^16 but they * provide setres*id32 variants that allow 2^32. * Others just let setres*id do 2^32 anyway. */ #ifdef SYS_setresgid32 #define OURSYS_setresgid SYS_setresgid32 #else #define OURSYS_setresgid SYS_setresgid #endif #ifdef SYS_setresuid32 #define OURSYS_setresuid SYS_setresuid32 #else #define OURSYS_setresuid SYS_setresuid #endif /* * Change to uid/gid of caller so that file is created with * ownership of caller. * TODO: What about selinux context? */ static int lo_change_cred(fuse_req_t req, struct lo_cred *old) { int res; old->euid = geteuid(); old->egid = getegid(); res = syscall(OURSYS_setresgid, -1, fuse_req_ctx(req)->gid, -1); if (res == -1) { return errno; } res = syscall(OURSYS_setresuid, -1, fuse_req_ctx(req)->uid, -1); if (res == -1) { int errno_save = errno; syscall(OURSYS_setresgid, -1, old->egid, -1); return errno_save; } return 0; } /* Regain Privileges */ static void lo_restore_cred(struct lo_cred *old) { int res; res = syscall(OURSYS_setresuid, -1, old->euid, -1); if (res == -1) { fuse_log(FUSE_LOG_ERR, "seteuid(%u): %m\n", old->euid); exit(1); } res = syscall(OURSYS_setresgid, -1, old->egid, -1); if (res == -1) { fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid); exit(1); } } static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, const char *name, mode_t mode, dev_t rdev, const char *link) { int res; int saverr; struct lo_data *lo = lo_data(req); struct lo_inode *dir; struct fuse_entry_param e; struct lo_cred old = {}; if (!is_safe_path_component(name)) { fuse_reply_err(req, EINVAL); return; } dir = lo_inode(req, parent); if (!dir) { fuse_reply_err(req, EBADF); return; } saverr = lo_change_cred(req, &old); if (saverr) { goto out; } res = mknod_wrapper(dir->fd, name, link, mode, rdev); saverr = errno; lo_restore_cred(&old); if (res == -1) { goto out; } saverr = lo_do_lookup(req, parent, name, &e); if (saverr) { goto out; } fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long long)parent, name, (unsigned long long)e.ino); fuse_reply_entry(req, &e); lo_inode_put(lo, &dir); return; out: lo_inode_put(lo, &dir); fuse_reply_err(req, saverr); } static void lo_mknod(fuse_req_t req, fuse_ino_t parent, const char *name, mode_t mode, dev_t rdev) { lo_mknod_symlink(req, parent, name, mode, rdev, NULL); } static void lo_mkdir(fuse_req_t req, fuse_ino_t parent, const char *name, mode_t mode) { lo_mknod_symlink(req, parent, name, S_IFDIR | mode, 0, NULL); } static void lo_symlink(fuse_req_t req, const char *link, fuse_ino_t parent, const char *name) { lo_mknod_symlink(req, parent, name, S_IFLNK, 0, link); } static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent, const char *name) { int res; struct lo_data *lo = lo_data(req); struct lo_inode *parent_inode; struct lo_inode *inode; struct fuse_entry_param e; char procname[64]; int saverr; if (!is_safe_path_component(name)) { fuse_reply_err(req, EINVAL); return; } parent_inode = lo_inode(req, parent); inode = lo_inode(req, ino); if (!parent_inode || !inode) { errno = EBADF; goto out_err; } memset(&e, 0, sizeof(struct fuse_entry_param)); e.attr_timeout = lo->timeout; e.entry_timeout = lo->timeout; sprintf(procname, "%i", inode->fd); res = linkat(lo->proc_self_fd, procname, parent_inode->fd, name, AT_SYMLINK_FOLLOW); if (res == -1) { goto out_err; } res = fstatat(inode->fd, "", &e.attr, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW); if (res == -1) { goto out_err; } pthread_mutex_lock(&lo->mutex); inode->nlookup++; pthread_mutex_unlock(&lo->mutex); e.ino = inode->fuse_ino; fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long long)parent, name, (unsigned long long)e.ino); fuse_reply_entry(req, &e); lo_inode_put(lo, &parent_inode); lo_inode_put(lo, &inode); return; out_err: saverr = errno; lo_inode_put(lo, &parent_inode); lo_inode_put(lo, &inode); fuse_reply_err(req, saverr); } /* Increments nlookup and caller must release refcount using lo_inode_put() */ static struct lo_inode *lookup_name(fuse_req_t req, fuse_ino_t parent, const char *name) { int res; struct stat attr; res = fstatat(lo_fd(req, parent), name, &attr, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW); if (res == -1) { return NULL; } return lo_find(lo_data(req), &attr); } static void lo_rmdir(fuse_req_t req, fuse_ino_t parent, const char *name) { int res; struct lo_inode *inode; struct lo_data *lo = lo_data(req); if (!is_safe_path_component(name)) { fuse_reply_err(req, EINVAL); return; } inode = lookup_name(req, parent, name); if (!inode) { fuse_reply_err(req, EIO); return; } res = unlinkat(lo_fd(req, parent), name, AT_REMOVEDIR); fuse_reply_err(req, res == -1 ? errno : 0); unref_inode_lolocked(lo, inode, 1); lo_inode_put(lo, &inode); } static void lo_rename(fuse_req_t req, fuse_ino_t parent, const char *name, fuse_ino_t newparent, const char *newname, unsigned int flags) { int res; struct lo_inode *parent_inode; struct lo_inode *newparent_inode; struct lo_inode *oldinode = NULL; struct lo_inode *newinode = NULL; struct lo_data *lo = lo_data(req); if (!is_safe_path_component(name) || !is_safe_path_component(newname)) { fuse_reply_err(req, EINVAL); return; } parent_inode = lo_inode(req, parent); newparent_inode = lo_inode(req, newparent); if (!parent_inode || !newparent_inode) { fuse_reply_err(req, EBADF); goto out; } oldinode = lookup_name(req, parent, name); newinode = lookup_name(req, newparent, newname); if (!oldinode) { fuse_reply_err(req, EIO); goto out; } if (flags) { #ifndef SYS_renameat2 fuse_reply_err(req, EINVAL); #else res = syscall(SYS_renameat2, parent_inode->fd, name, newparent_inode->fd, newname, flags); if (res == -1 && errno == ENOSYS) { fuse_reply_err(req, EINVAL); } else { fuse_reply_err(req, res == -1 ? errno : 0); } #endif goto out; } res = renameat(parent_inode->fd, name, newparent_inode->fd, newname); fuse_reply_err(req, res == -1 ? errno : 0); out: unref_inode_lolocked(lo, oldinode, 1); unref_inode_lolocked(lo, newinode, 1); lo_inode_put(lo, &oldinode); lo_inode_put(lo, &newinode); lo_inode_put(lo, &parent_inode); lo_inode_put(lo, &newparent_inode); } static void lo_unlink(fuse_req_t req, fuse_ino_t parent, const char *name) { int res; struct lo_inode *inode; struct lo_data *lo = lo_data(req); if (!is_safe_path_component(name)) { fuse_reply_err(req, EINVAL); return; } inode = lookup_name(req, parent, name); if (!inode) { fuse_reply_err(req, EIO); return; } res = unlinkat(lo_fd(req, parent), name, 0); fuse_reply_err(req, res == -1 ? errno : 0); unref_inode_lolocked(lo, inode, 1); lo_inode_put(lo, &inode); } /* To be called with lo->mutex held */ static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n) { if (!inode) { return; } assert(inode->nlookup >= n); inode->nlookup -= n; if (!inode->nlookup) { lo_map_remove(&lo->ino_map, inode->fuse_ino); g_hash_table_remove(lo->inodes, &inode->key); if (g_hash_table_size(inode->posix_locks)) { fuse_log(FUSE_LOG_WARNING, "Hash table is not empty\n"); } g_hash_table_destroy(inode->posix_locks); pthread_mutex_destroy(&inode->plock_mutex); /* Drop our refcount from lo_do_lookup() */ lo_inode_put(lo, &inode); } } static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode, uint64_t n) { if (!inode) { return; } pthread_mutex_lock(&lo->mutex); unref_inode(lo, inode, n); pthread_mutex_unlock(&lo->mutex); } static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup) { struct lo_data *lo = lo_data(req); struct lo_inode *inode; inode = lo_inode(req, ino); if (!inode) { return; } fuse_log(FUSE_LOG_DEBUG, " forget %lli %lli -%lli\n", (unsigned long long)ino, (unsigned long long)inode->nlookup, (unsigned long long)nlookup); unref_inode_lolocked(lo, inode, nlookup); lo_inode_put(lo, &inode); } static void lo_forget(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup) { lo_forget_one(req, ino, nlookup); fuse_reply_none(req); } static void lo_forget_multi(fuse_req_t req, size_t count, struct fuse_forget_data *forgets) { int i; for (i = 0; i < count; i++) { lo_forget_one(req, forgets[i].ino, forgets[i].nlookup); } fuse_reply_none(req); } static void lo_readlink(fuse_req_t req, fuse_ino_t ino) { char buf[PATH_MAX + 1]; int res; res = readlinkat(lo_fd(req, ino), "", buf, sizeof(buf)); if (res == -1) { return (void)fuse_reply_err(req, errno); } if (res == sizeof(buf)) { return (void)fuse_reply_err(req, ENAMETOOLONG); } buf[res] = '\0'; fuse_reply_readlink(req, buf); } struct lo_dirp { gint refcount; DIR *dp; struct dirent *entry; off_t offset; }; static void lo_dirp_put(struct lo_dirp **dp) { struct lo_dirp *d = *dp; if (!d) { return; } *dp = NULL; if (g_atomic_int_dec_and_test(&d->refcount)) { closedir(d->dp); free(d); } } /* Call lo_dirp_put() on the return value when no longer needed */ static struct lo_dirp *lo_dirp(fuse_req_t req, struct fuse_file_info *fi) { struct lo_data *lo = lo_data(req); struct lo_map_elem *elem; pthread_mutex_lock(&lo->mutex); elem = lo_map_get(&lo->dirp_map, fi->fh); if (elem) { g_atomic_int_inc(&elem->dirp->refcount); } pthread_mutex_unlock(&lo->mutex); if (!elem) { return NULL; } return elem->dirp; } static void lo_opendir(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) { int error = ENOMEM; struct lo_data *lo = lo_data(req); struct lo_dirp *d; int fd; ssize_t fh; d = calloc(1, sizeof(struct lo_dirp)); if (d == NULL) { goto out_err; } fd = openat(lo_fd(req, ino), ".", O_RDONLY); if (fd == -1) { goto out_errno; } d->dp = fdopendir(fd); if (d->dp == NULL) { goto out_errno; } d->offset = 0; d->entry = NULL; g_atomic_int_set(&d->refcount, 1); /* paired with lo_releasedir() */ pthread_mutex_lock(&lo->mutex); fh = lo_add_dirp_mapping(req, d); pthread_mutex_unlock(&lo->mutex); if (fh == -1) { goto out_err; } fi->fh = fh; if (lo->cache == CACHE_ALWAYS) { fi->cache_readdir = 1; } fuse_reply_open(req, fi); return; out_errno: error = errno; out_err: if (d) { if (d->dp) { closedir(d->dp); } else if (fd != -1) { close(fd); } free(d); } fuse_reply_err(req, error); } static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset, struct fuse_file_info *fi, int plus) { struct lo_data *lo = lo_data(req); struct lo_dirp *d = NULL; struct lo_inode *dinode; char *buf = NULL; char *p; size_t rem = size; int err = EBADF; dinode = lo_inode(req, ino); if (!dinode) { goto error; } d = lo_dirp(req, fi); if (!d) { goto error; } err = ENOMEM; buf = calloc(1, size); if (!buf) { goto error; } p = buf; if (offset != d->offset) { seekdir(d->dp, offset); d->entry = NULL; d->offset = offset; } while (1) { size_t entsize; off_t nextoff; const char *name; if (!d->entry) { errno = 0; d->entry = readdir(d->dp); if (!d->entry) { if (errno) { /* Error */ err = errno; goto error; } else { /* End of stream */ break; } } } nextoff = d->entry->d_off; name = d->entry->d_name; fuse_ino_t entry_ino = 0; struct fuse_entry_param e = (struct fuse_entry_param){ .attr.st_ino = d->entry->d_ino, .attr.st_mode = d->entry->d_type << 12, }; /* Hide root's parent directory */ if (dinode == &lo->root && strcmp(name, "..") == 0) { e.attr.st_ino = lo->root.key.ino; e.attr.st_mode = DT_DIR << 12; } if (plus) { if (!is_dot_or_dotdot(name)) { err = lo_do_lookup(req, ino, name, &e); if (err) { goto error; } entry_ino = e.ino; } entsize = fuse_add_direntry_plus(req, p, rem, name, &e, nextoff); } else { entsize = fuse_add_direntry(req, p, rem, name, &e.attr, nextoff); } if (entsize > rem) { if (entry_ino != 0) { lo_forget_one(req, entry_ino, 1); } break; } p += entsize; rem -= entsize; d->entry = NULL; d->offset = nextoff; } err = 0; error: lo_dirp_put(&d); lo_inode_put(lo, &dinode); /* * If there's an error, we can only signal it if we haven't stored * any entries yet - otherwise we'd end up with wrong lookup * counts for the entries that are already in the buffer. So we * return what we've collected until that point. */ if (err && rem == size) { fuse_reply_err(req, err); } else { fuse_reply_buf(req, buf, size - rem); } free(buf); } static void lo_readdir(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset, struct fuse_file_info *fi) { lo_do_readdir(req, ino, size, offset, fi, 0); } static void lo_readdirplus(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset, struct fuse_file_info *fi) { lo_do_readdir(req, ino, size, offset, fi, 1); } static void lo_releasedir(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) { struct lo_data *lo = lo_data(req); struct lo_map_elem *elem; struct lo_dirp *d; (void)ino; pthread_mutex_lock(&lo->mutex); elem = lo_map_get(&lo->dirp_map, fi->fh); if (!elem) { pthread_mutex_unlock(&lo->mutex); fuse_reply_err(req, EBADF); return; } d = elem->dirp; lo_map_remove(&lo->dirp_map, fi->fh); pthread_mutex_unlock(&lo->mutex); lo_dirp_put(&d); /* paired with lo_opendir() */ fuse_reply_err(req, 0); } static void update_open_flags(int writeback, int allow_direct_io, struct fuse_file_info *fi) { /* * With writeback cache, kernel may send read requests even * when userspace opened write-only */ if (writeback && (fi->flags & O_ACCMODE) == O_WRONLY) { fi->flags &= ~O_ACCMODE; fi->flags |= O_RDWR; } /* * With writeback cache, O_APPEND is handled by the kernel. * This breaks atomicity (since the file may change in the * underlying filesystem, so that the kernel's idea of the * end of the file isn't accurate anymore). In this example, * we just accept that. A more rigorous filesystem may want * to return an error here */ if (writeback && (fi->flags & O_APPEND)) { fi->flags &= ~O_APPEND; } /* * O_DIRECT in guest should not necessarily mean bypassing page * cache on host as well. Therefore, we discard it by default * ('-o no_allow_direct_io'). If somebody needs that behavior, * the '-o allow_direct_io' option should be set. */ if (!allow_direct_io) { fi->flags &= ~O_DIRECT; } } static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, mode_t mode, struct fuse_file_info *fi) { int fd; struct lo_data *lo = lo_data(req); struct lo_inode *parent_inode; struct fuse_entry_param e; int err; struct lo_cred old = {}; fuse_log(FUSE_LOG_DEBUG, "lo_create(parent=%" PRIu64 ", name=%s)\n", parent, name); if (!is_safe_path_component(name)) { fuse_reply_err(req, EINVAL); return; } parent_inode = lo_inode(req, parent); if (!parent_inode) { fuse_reply_err(req, EBADF); return; } err = lo_change_cred(req, &old); if (err) { goto out; } update_open_flags(lo->writeback, lo->allow_direct_io, fi); fd = openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOLLOW, mode); err = fd == -1 ? errno : 0; lo_restore_cred(&old); if (!err) { ssize_t fh; pthread_mutex_lock(&lo->mutex); fh = lo_add_fd_mapping(req, fd); pthread_mutex_unlock(&lo->mutex); if (fh == -1) { close(fd); err = ENOMEM; goto out; } fi->fh = fh; err = lo_do_lookup(req, parent, name, &e); } if (lo->cache == CACHE_NONE) { fi->direct_io = 1; } else if (lo->cache == CACHE_ALWAYS) { fi->keep_cache = 1; } out: lo_inode_put(lo, &parent_inode); if (err) { fuse_reply_err(req, err); } else { fuse_reply_create(req, &e, fi); } } /* Should be called with inode->plock_mutex held */ static struct lo_inode_plock *lookup_create_plock_ctx(struct lo_data *lo, struct lo_inode *inode, uint64_t lock_owner, pid_t pid, int *err) { struct lo_inode_plock *plock; char procname[64]; int fd; plock = g_hash_table_lookup(inode->posix_locks, GUINT_TO_POINTER(lock_owner)); if (plock) { return plock; } plock = malloc(sizeof(struct lo_inode_plock)); if (!plock) { *err = ENOMEM; return NULL; } /* Open another instance of file which can be used for ofd locks. */ sprintf(procname, "%i", inode->fd); /* TODO: What if file is not writable? */ fd = openat(lo->proc_self_fd, procname, O_RDWR); if (fd == -1) { *err = errno; free(plock); return NULL; } plock->lock_owner = lock_owner; plock->fd = fd; g_hash_table_insert(inode->posix_locks, GUINT_TO_POINTER(plock->lock_owner), plock); return plock; } static void lo_getlk(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi, struct flock *lock) { struct lo_data *lo = lo_data(req); struct lo_inode *inode; struct lo_inode_plock *plock; int ret, saverr = 0; fuse_log(FUSE_LOG_DEBUG, "lo_getlk(ino=%" PRIu64 ", flags=%d)" " owner=0x%lx, l_type=%d l_start=0x%lx" " l_len=0x%lx\n", ino, fi->flags, fi->lock_owner, lock->l_type, lock->l_start, lock->l_len); inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); return; } pthread_mutex_lock(&inode->plock_mutex); plock = lookup_create_plock_ctx(lo, inode, fi->lock_owner, lock->l_pid, &ret); if (!plock) { saverr = ret; goto out; } ret = fcntl(plock->fd, F_OFD_GETLK, lock); if (ret == -1) { saverr = errno; } out: pthread_mutex_unlock(&inode->plock_mutex); lo_inode_put(lo, &inode); if (saverr) { fuse_reply_err(req, saverr); } else { fuse_reply_lock(req, lock); } } static void lo_setlk(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi, struct flock *lock, int sleep) { struct lo_data *lo = lo_data(req); struct lo_inode *inode; struct lo_inode_plock *plock; int ret, saverr = 0; fuse_log(FUSE_LOG_DEBUG, "lo_setlk(ino=%" PRIu64 ", flags=%d)" " cmd=%d pid=%d owner=0x%lx sleep=%d l_whence=%d" " l_start=0x%lx l_len=0x%lx\n", ino, fi->flags, lock->l_type, lock->l_pid, fi->lock_owner, sleep, lock->l_whence, lock->l_start, lock->l_len); if (sleep) { fuse_reply_err(req, EOPNOTSUPP); return; } inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); return; } pthread_mutex_lock(&inode->plock_mutex); plock = lookup_create_plock_ctx(lo, inode, fi->lock_owner, lock->l_pid, &ret); if (!plock) { saverr = ret; goto out; } /* TODO: Is it alright to modify flock? */ lock->l_pid = 0; ret = fcntl(plock->fd, F_OFD_SETLK, lock); if (ret == -1) { saverr = errno; } out: pthread_mutex_unlock(&inode->plock_mutex); lo_inode_put(lo, &inode); fuse_reply_err(req, saverr); } static void lo_fsyncdir(fuse_req_t req, fuse_ino_t ino, int datasync, struct fuse_file_info *fi) { int res; struct lo_dirp *d; int fd; (void)ino; d = lo_dirp(req, fi); if (!d) { fuse_reply_err(req, EBADF); return; } fd = dirfd(d->dp); if (datasync) { res = fdatasync(fd); } else { res = fsync(fd); } lo_dirp_put(&d); fuse_reply_err(req, res == -1 ? errno : 0); } static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) { int fd; ssize_t fh; char buf[64]; struct lo_data *lo = lo_data(req); fuse_log(FUSE_LOG_DEBUG, "lo_open(ino=%" PRIu64 ", flags=%d)\n", ino, fi->flags); update_open_flags(lo->writeback, lo->allow_direct_io, fi); sprintf(buf, "%i", lo_fd(req, ino)); fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW); if (fd == -1) { return (void)fuse_reply_err(req, errno); } pthread_mutex_lock(&lo->mutex); fh = lo_add_fd_mapping(req, fd); pthread_mutex_unlock(&lo->mutex); if (fh == -1) { close(fd); fuse_reply_err(req, ENOMEM); return; } fi->fh = fh; if (lo->cache == CACHE_NONE) { fi->direct_io = 1; } else if (lo->cache == CACHE_ALWAYS) { fi->keep_cache = 1; } fuse_reply_open(req, fi); } static void lo_release(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) { struct lo_data *lo = lo_data(req); struct lo_map_elem *elem; int fd = -1; (void)ino; pthread_mutex_lock(&lo->mutex); elem = lo_map_get(&lo->fd_map, fi->fh); if (elem) { fd = elem->fd; elem = NULL; lo_map_remove(&lo->fd_map, fi->fh); } pthread_mutex_unlock(&lo->mutex); close(fd); fuse_reply_err(req, 0); } static void lo_flush(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) { int res; (void)ino; struct lo_inode *inode; inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); return; } /* An fd is going away. Cleanup associated posix locks */ pthread_mutex_lock(&inode->plock_mutex); g_hash_table_remove(inode->posix_locks, GUINT_TO_POINTER(fi->lock_owner)); pthread_mutex_unlock(&inode->plock_mutex); res = close(dup(lo_fi_fd(req, fi))); lo_inode_put(lo_data(req), &inode); fuse_reply_err(req, res == -1 ? errno : 0); } static void lo_fsync(fuse_req_t req, fuse_ino_t ino, int datasync, struct fuse_file_info *fi) { int res; int fd; char *buf; fuse_log(FUSE_LOG_DEBUG, "lo_fsync(ino=%" PRIu64 ", fi=0x%p)\n", ino, (void *)fi); if (!fi) { struct lo_data *lo = lo_data(req); res = asprintf(&buf, "%i", lo_fd(req, ino)); if (res == -1) { return (void)fuse_reply_err(req, errno); } fd = openat(lo->proc_self_fd, buf, O_RDWR); free(buf); if (fd == -1) { return (void)fuse_reply_err(req, errno); } } else { fd = lo_fi_fd(req, fi); } if (datasync) { res = fdatasync(fd); } else { res = fsync(fd); } if (!fi) { close(fd); } fuse_reply_err(req, res == -1 ? errno : 0); } static void lo_read(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset, struct fuse_file_info *fi) { struct fuse_bufvec buf = FUSE_BUFVEC_INIT(size); fuse_log(FUSE_LOG_DEBUG, "lo_read(ino=%" PRIu64 ", size=%zd, " "off=%lu)\n", ino, size, (unsigned long)offset); buf.buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK; buf.buf[0].fd = lo_fi_fd(req, fi); buf.buf[0].pos = offset; fuse_reply_data(req, &buf); } static void lo_write_buf(fuse_req_t req, fuse_ino_t ino, struct fuse_bufvec *in_buf, off_t off, struct fuse_file_info *fi) { (void)ino; ssize_t res; struct fuse_bufvec out_buf = FUSE_BUFVEC_INIT(fuse_buf_size(in_buf)); bool cap_fsetid_dropped = false; out_buf.buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK; out_buf.buf[0].fd = lo_fi_fd(req, fi); out_buf.buf[0].pos = off; fuse_log(FUSE_LOG_DEBUG, "lo_write_buf(ino=%" PRIu64 ", size=%zd, off=%lu)\n", ino, out_buf.buf[0].size, (unsigned long)off); /* * If kill_priv is set, drop CAP_FSETID which should lead to kernel * clearing setuid/setgid on file. */ if (fi->kill_priv) { res = drop_effective_cap("FSETID", &cap_fsetid_dropped); if (res != 0) { fuse_reply_err(req, res); return; } } res = fuse_buf_copy(&out_buf, in_buf); if (res < 0) { fuse_reply_err(req, -res); } else { fuse_reply_write(req, (size_t)res); } if (cap_fsetid_dropped) { res = gain_effective_cap("FSETID"); if (res) { fuse_log(FUSE_LOG_ERR, "Failed to gain CAP_FSETID\n"); } } } static void lo_statfs(fuse_req_t req, fuse_ino_t ino) { int res; struct statvfs stbuf; res = fstatvfs(lo_fd(req, ino), &stbuf); if (res == -1) { fuse_reply_err(req, errno); } else { fuse_reply_statfs(req, &stbuf); } } static void lo_fallocate(fuse_req_t req, fuse_ino_t ino, int mode, off_t offset, off_t length, struct fuse_file_info *fi) { int err = EOPNOTSUPP; (void)ino; #ifdef CONFIG_FALLOCATE err = fallocate(lo_fi_fd(req, fi), mode, offset, length); if (err < 0) { err = errno; } #elif defined(CONFIG_POSIX_FALLOCATE) if (mode) { fuse_reply_err(req, EOPNOTSUPP); return; } err = posix_fallocate(lo_fi_fd(req, fi), offset, length); #endif fuse_reply_err(req, err); } static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi, int op) { int res; (void)ino; res = flock(lo_fi_fd(req, fi), op); fuse_reply_err(req, res == -1 ? errno : 0); } static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name, size_t size) { struct lo_data *lo = lo_data(req); char *value = NULL; char procname[64]; struct lo_inode *inode; ssize_t ret; int saverr; int fd = -1; inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); return; } saverr = ENOSYS; if (!lo_data(req)->xattr) { goto out; } fuse_log(FUSE_LOG_DEBUG, "lo_getxattr(ino=%" PRIu64 ", name=%s size=%zd)\n", ino, name, size); if (size) { value = malloc(size); if (!value) { goto out_err; } } sprintf(procname, "%i", inode->fd); /* * It is not safe to open() non-regular/non-dir files in file server * unless O_PATH is used, so use that method for regular files/dir * only (as it seems giving less performance overhead). * Otherwise, call fchdir() to avoid open(). */ if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) { fd = openat(lo->proc_self_fd, procname, O_RDONLY); if (fd < 0) { goto out_err; } ret = fgetxattr(fd, name, value, size); } else { /* fchdir should not fail here */ assert(fchdir(lo->proc_self_fd) == 0); ret = getxattr(procname, name, value, size); assert(fchdir(lo->root.fd) == 0); } if (ret == -1) { goto out_err; } if (size) { saverr = 0; if (ret == 0) { goto out; } fuse_reply_buf(req, value, ret); } else { fuse_reply_xattr(req, ret); } out_free: free(value); if (fd >= 0) { close(fd); } lo_inode_put(lo, &inode); return; out_err: saverr = errno; out: fuse_reply_err(req, saverr); goto out_free; } static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) { struct lo_data *lo = lo_data(req); char *value = NULL; char procname[64]; struct lo_inode *inode; ssize_t ret; int saverr; int fd = -1; inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); return; } saverr = ENOSYS; if (!lo_data(req)->xattr) { goto out; } fuse_log(FUSE_LOG_DEBUG, "lo_listxattr(ino=%" PRIu64 ", size=%zd)\n", ino, size); if (size) { value = malloc(size); if (!value) { goto out_err; } } sprintf(procname, "%i", inode->fd); if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) { fd = openat(lo->proc_self_fd, procname, O_RDONLY); if (fd < 0) { goto out_err; } ret = flistxattr(fd, value, size); } else { /* fchdir should not fail here */ assert(fchdir(lo->proc_self_fd) == 0); ret = listxattr(procname, value, size); assert(fchdir(lo->root.fd) == 0); } if (ret == -1) { goto out_err; } if (size) { saverr = 0; if (ret == 0) { goto out; } fuse_reply_buf(req, value, ret); } else { fuse_reply_xattr(req, ret); } out_free: free(value); if (fd >= 0) { close(fd); } lo_inode_put(lo, &inode); return; out_err: saverr = errno; out: fuse_reply_err(req, saverr); goto out_free; } static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name, const char *value, size_t size, int flags) { char procname[64]; struct lo_data *lo = lo_data(req); struct lo_inode *inode; ssize_t ret; int saverr; int fd = -1; inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); return; } saverr = ENOSYS; if (!lo_data(req)->xattr) { goto out; } fuse_log(FUSE_LOG_DEBUG, "lo_setxattr(ino=%" PRIu64 ", name=%s value=%s size=%zd)\n", ino, name, value, size); sprintf(procname, "%i", inode->fd); if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) { fd = openat(lo->proc_self_fd, procname, O_RDONLY); if (fd < 0) { saverr = errno; goto out; } ret = fsetxattr(fd, name, value, size, flags); } else { /* fchdir should not fail here */ assert(fchdir(lo->proc_self_fd) == 0); ret = setxattr(procname, name, value, size, flags); assert(fchdir(lo->root.fd) == 0); } saverr = ret == -1 ? errno : 0; out: if (fd >= 0) { close(fd); } lo_inode_put(lo, &inode); fuse_reply_err(req, saverr); } static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name) { char procname[64]; struct lo_data *lo = lo_data(req); struct lo_inode *inode; ssize_t ret; int saverr; int fd = -1; inode = lo_inode(req, ino); if (!inode) { fuse_reply_err(req, EBADF); return; } saverr = ENOSYS; if (!lo_data(req)->xattr) { goto out; } fuse_log(FUSE_LOG_DEBUG, "lo_removexattr(ino=%" PRIu64 ", name=%s)\n", ino, name); sprintf(procname, "%i", inode->fd); if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) { fd = openat(lo->proc_self_fd, procname, O_RDONLY); if (fd < 0) { saverr = errno; goto out; } ret = fremovexattr(fd, name); } else { /* fchdir should not fail here */ assert(fchdir(lo->proc_self_fd) == 0); ret = removexattr(procname, name); assert(fchdir(lo->root.fd) == 0); } saverr = ret == -1 ? errno : 0; out: if (fd >= 0) { close(fd); } lo_inode_put(lo, &inode); fuse_reply_err(req, saverr); } #ifdef HAVE_COPY_FILE_RANGE static void lo_copy_file_range(fuse_req_t req, fuse_ino_t ino_in, off_t off_in, struct fuse_file_info *fi_in, fuse_ino_t ino_out, off_t off_out, struct fuse_file_info *fi_out, size_t len, int flags) { int in_fd, out_fd; ssize_t res; in_fd = lo_fi_fd(req, fi_in); out_fd = lo_fi_fd(req, fi_out); fuse_log(FUSE_LOG_DEBUG, "lo_copy_file_range(ino=%" PRIu64 "/fd=%d, " "off=%lu, ino=%" PRIu64 "/fd=%d, " "off=%lu, size=%zd, flags=0x%x)\n", ino_in, in_fd, off_in, ino_out, out_fd, off_out, len, flags); res = copy_file_range(in_fd, &off_in, out_fd, &off_out, len, flags); if (res < 0) { fuse_reply_err(req, errno); } else { fuse_reply_write(req, res); } } #endif static void lo_lseek(fuse_req_t req, fuse_ino_t ino, off_t off, int whence, struct fuse_file_info *fi) { off_t res; (void)ino; res = lseek(lo_fi_fd(req, fi), off, whence); if (res != -1) { fuse_reply_lseek(req, res); } else { fuse_reply_err(req, errno); } } static void lo_destroy(void *userdata) { struct lo_data *lo = (struct lo_data *)userdata; pthread_mutex_lock(&lo->mutex); while (true) { GHashTableIter iter; gpointer key, value; g_hash_table_iter_init(&iter, lo->inodes); if (!g_hash_table_iter_next(&iter, &key, &value)) { break; } struct lo_inode *inode = value; unref_inode(lo, inode, inode->nlookup); } pthread_mutex_unlock(&lo->mutex); } static struct fuse_lowlevel_ops lo_oper = { .init = lo_init, .lookup = lo_lookup, .mkdir = lo_mkdir, .mknod = lo_mknod, .symlink = lo_symlink, .link = lo_link, .unlink = lo_unlink, .rmdir = lo_rmdir, .rename = lo_rename, .forget = lo_forget, .forget_multi = lo_forget_multi, .getattr = lo_getattr, .setattr = lo_setattr, .readlink = lo_readlink, .opendir = lo_opendir, .readdir = lo_readdir, .readdirplus = lo_readdirplus, .releasedir = lo_releasedir, .fsyncdir = lo_fsyncdir, .create = lo_create, .getlk = lo_getlk, .setlk = lo_setlk, .open = lo_open, .release = lo_release, .flush = lo_flush, .fsync = lo_fsync, .read = lo_read, .write_buf = lo_write_buf, .statfs = lo_statfs, .fallocate = lo_fallocate, .flock = lo_flock, .getxattr = lo_getxattr, .listxattr = lo_listxattr, .setxattr = lo_setxattr, .removexattr = lo_removexattr, #ifdef HAVE_COPY_FILE_RANGE .copy_file_range = lo_copy_file_range, #endif .lseek = lo_lseek, .destroy = lo_destroy, }; /* Print vhost-user.json backend program capabilities */ static void print_capabilities(void) { printf("{\n"); printf(" \"type\": \"fs\"\n"); printf("}\n"); } /* * Drop all Linux capabilities because the wait parent process only needs to * sit in waitpid(2) and terminate. */ static void setup_wait_parent_capabilities(void) { capng_setpid(syscall(SYS_gettid)); capng_clear(CAPNG_SELECT_BOTH); capng_apply(CAPNG_SELECT_BOTH); } /* * Move to a new mount, net, and pid namespaces to isolate this process. */ static void setup_namespaces(struct lo_data *lo, struct fuse_session *se) { pid_t child; char template[] = "virtiofsd-XXXXXX"; char *tmpdir; /* * Create a new pid namespace for *child* processes. We'll have to * fork in order to enter the new pid namespace. A new mount namespace * is also needed so that we can remount /proc for the new pid * namespace. * * Our UNIX domain sockets have been created. Now we can move to * an empty network namespace to prevent TCP/IP and other network * activity in case this process is compromised. */ if (unshare(CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWNET) != 0) { fuse_log(FUSE_LOG_ERR, "unshare(CLONE_NEWPID | CLONE_NEWNS): %m\n"); exit(1); } child = fork(); if (child < 0) { fuse_log(FUSE_LOG_ERR, "fork() failed: %m\n"); exit(1); } if (child > 0) { pid_t waited; int wstatus; setup_wait_parent_capabilities(); /* The parent waits for the child */ do { waited = waitpid(child, &wstatus, 0); } while (waited < 0 && errno == EINTR && !se->exited); /* We were terminated by a signal, see fuse_signals.c */ if (se->exited) { exit(0); } if (WIFEXITED(wstatus)) { exit(WEXITSTATUS(wstatus)); } exit(1); } /* Send us SIGTERM when the parent thread terminates, see prctl(2) */ prctl(PR_SET_PDEATHSIG, SIGTERM); /* * If the mounts have shared propagation then we want to opt out so our * mount changes don't affect the parent mount namespace. */ if (mount(NULL, "/", NULL, MS_REC | MS_SLAVE, NULL) < 0) { fuse_log(FUSE_LOG_ERR, "mount(/, MS_REC|MS_SLAVE): %m\n"); exit(1); } /* The child must remount /proc to use the new pid namespace */ if (mount("proc", "/proc", "proc", MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) { fuse_log(FUSE_LOG_ERR, "mount(/proc): %m\n"); exit(1); } tmpdir = mkdtemp(template); if (!tmpdir) { fuse_log(FUSE_LOG_ERR, "tmpdir(%s): %m\n", template); exit(1); } if (mount("/proc/self/fd", tmpdir, NULL, MS_BIND, NULL) < 0) { fuse_log(FUSE_LOG_ERR, "mount(/proc/self/fd, %s, MS_BIND): %m\n", tmpdir); exit(1); } /* Now we can get our /proc/self/fd directory file descriptor */ lo->proc_self_fd = open(tmpdir, O_PATH); if (lo->proc_self_fd == -1) { fuse_log(FUSE_LOG_ERR, "open(%s, O_PATH): %m\n", tmpdir); exit(1); } if (umount2(tmpdir, MNT_DETACH) < 0) { fuse_log(FUSE_LOG_ERR, "umount2(%s, MNT_DETACH): %m\n", tmpdir); exit(1); } if (rmdir(tmpdir) < 0) { fuse_log(FUSE_LOG_ERR, "rmdir(%s): %m\n", tmpdir); } } /* * Capture the capability state, we'll need to restore this for individual * threads later; see load_capng. */ static void setup_capng(void) { /* Note this accesses /proc so has to happen before the sandbox */ if (capng_get_caps_process()) { fuse_log(FUSE_LOG_ERR, "capng_get_caps_process\n"); exit(1); } pthread_mutex_init(&cap.mutex, NULL); pthread_mutex_lock(&cap.mutex); cap.saved = capng_save_state(); if (!cap.saved) { fuse_log(FUSE_LOG_ERR, "capng_save_state\n"); exit(1); } pthread_mutex_unlock(&cap.mutex); } static void cleanup_capng(void) { free(cap.saved); cap.saved = NULL; pthread_mutex_destroy(&cap.mutex); } /* * Make the source directory our root so symlinks cannot escape and no other * files are accessible. Assumes unshare(CLONE_NEWNS) was already called. */ static void setup_mounts(const char *source) { int oldroot; int newroot; if (mount(source, source, NULL, MS_BIND | MS_REC, NULL) < 0) { fuse_log(FUSE_LOG_ERR, "mount(%s, %s, MS_BIND): %m\n", source, source); exit(1); } /* This magic is based on lxc's lxc_pivot_root() */ oldroot = open("/", O_DIRECTORY | O_RDONLY | O_CLOEXEC); if (oldroot < 0) { fuse_log(FUSE_LOG_ERR, "open(/): %m\n"); exit(1); } newroot = open(source, O_DIRECTORY | O_RDONLY | O_CLOEXEC); if (newroot < 0) { fuse_log(FUSE_LOG_ERR, "open(%s): %m\n", source); exit(1); } if (fchdir(newroot) < 0) { fuse_log(FUSE_LOG_ERR, "fchdir(newroot): %m\n"); exit(1); } if (syscall(__NR_pivot_root, ".", ".") < 0) { fuse_log(FUSE_LOG_ERR, "pivot_root(., .): %m\n"); exit(1); } if (fchdir(oldroot) < 0) { fuse_log(FUSE_LOG_ERR, "fchdir(oldroot): %m\n"); exit(1); } if (mount("", ".", "", MS_SLAVE | MS_REC, NULL) < 0) { fuse_log(FUSE_LOG_ERR, "mount(., MS_SLAVE | MS_REC): %m\n"); exit(1); } if (umount2(".", MNT_DETACH) < 0) { fuse_log(FUSE_LOG_ERR, "umount2(., MNT_DETACH): %m\n"); exit(1); } if (fchdir(newroot) < 0) { fuse_log(FUSE_LOG_ERR, "fchdir(newroot): %m\n"); exit(1); } close(newroot); close(oldroot); } /* * Only keep whitelisted capabilities that are needed for file system operation * The (possibly NULL) modcaps_in string passed in is free'd before exit. */ static void setup_capabilities(char *modcaps_in) { char *modcaps = modcaps_in; pthread_mutex_lock(&cap.mutex); capng_restore_state(&cap.saved); /* * Whitelist file system-related capabilities that are needed for a file * server to act like root. Drop everything else like networking and * sysadmin capabilities. * * Exclusions: * 1. CAP_LINUX_IMMUTABLE is not included because it's only used via ioctl * and we don't support that. * 2. CAP_MAC_OVERRIDE is not included because it only seems to be * used by the Smack LSM. Omit it until there is demand for it. */ capng_setpid(syscall(SYS_gettid)); capng_clear(CAPNG_SELECT_BOTH); if (capng_updatev(CAPNG_ADD, CAPNG_PERMITTED | CAPNG_EFFECTIVE, CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_FOWNER, CAP_FSETID, CAP_SETGID, CAP_SETUID, CAP_MKNOD, CAP_SETFCAP, -1)) { fuse_log(FUSE_LOG_ERR, "%s: capng_updatev failed\n", __func__); exit(1); } /* * The modcaps option is a colon separated list of caps, * each preceded by either + or -. */ while (modcaps) { capng_act_t action; int cap; char *next = strchr(modcaps, ':'); if (next) { *next = '\0'; next++; } switch (modcaps[0]) { case '+': action = CAPNG_ADD; break; case '-': action = CAPNG_DROP; break; default: fuse_log(FUSE_LOG_ERR, "%s: Expecting '+'/'-' in modcaps but found '%c'\n", __func__, modcaps[0]); exit(1); } cap = capng_name_to_capability(modcaps + 1); if (cap < 0) { fuse_log(FUSE_LOG_ERR, "%s: Unknown capability '%s'\n", __func__, modcaps); exit(1); } if (capng_update(action, CAPNG_PERMITTED | CAPNG_EFFECTIVE, cap)) { fuse_log(FUSE_LOG_ERR, "%s: capng_update failed for '%s'\n", __func__, modcaps); exit(1); } modcaps = next; } g_free(modcaps_in); if (capng_apply(CAPNG_SELECT_BOTH)) { fuse_log(FUSE_LOG_ERR, "%s: capng_apply failed\n", __func__); exit(1); } cap.saved = capng_save_state(); if (!cap.saved) { fuse_log(FUSE_LOG_ERR, "%s: capng_save_state failed\n", __func__); exit(1); } pthread_mutex_unlock(&cap.mutex); } /* * Lock down this process to prevent access to other processes or files outside * source directory. This reduces the impact of arbitrary code execution bugs. */ static void setup_sandbox(struct lo_data *lo, struct fuse_session *se, bool enable_syslog) { setup_namespaces(lo, se); setup_mounts(lo->source); setup_seccomp(enable_syslog); setup_capabilities(g_strdup(lo->modcaps)); } /* Set the maximum number of open file descriptors */ static void setup_nofile_rlimit(unsigned long rlimit_nofile) { struct rlimit rlim = { .rlim_cur = rlimit_nofile, .rlim_max = rlimit_nofile, }; if (rlimit_nofile == 0) { return; /* nothing to do */ } if (setrlimit(RLIMIT_NOFILE, &rlim) < 0) { /* Ignore SELinux denials */ if (errno == EPERM) { return; } fuse_log(FUSE_LOG_ERR, "setrlimit(RLIMIT_NOFILE): %m\n"); exit(1); } } static void log_func(enum fuse_log_level level, const char *fmt, va_list ap) { g_autofree char *localfmt = NULL; if (current_log_level < level) { return; } if (current_log_level == FUSE_LOG_DEBUG) { if (!use_syslog) { localfmt = g_strdup_printf("[%" PRId64 "] [ID: %08ld] %s", get_clock(), syscall(__NR_gettid), fmt); } else { localfmt = g_strdup_printf("[ID: %08ld] %s", syscall(__NR_gettid), fmt); } fmt = localfmt; } if (use_syslog) { int priority = LOG_ERR; switch (level) { case FUSE_LOG_EMERG: priority = LOG_EMERG; break; case FUSE_LOG_ALERT: priority = LOG_ALERT; break; case FUSE_LOG_CRIT: priority = LOG_CRIT; break; case FUSE_LOG_ERR: priority = LOG_ERR; break; case FUSE_LOG_WARNING: priority = LOG_WARNING; break; case FUSE_LOG_NOTICE: priority = LOG_NOTICE; break; case FUSE_LOG_INFO: priority = LOG_INFO; break; case FUSE_LOG_DEBUG: priority = LOG_DEBUG; break; } vsyslog(priority, fmt, ap); } else { vfprintf(stderr, fmt, ap); } } static void setup_root(struct lo_data *lo, struct lo_inode *root) { int fd, res; struct stat stat; fd = open("/", O_PATH); if (fd == -1) { fuse_log(FUSE_LOG_ERR, "open(%s, O_PATH): %m\n", lo->source); exit(1); } res = fstatat(fd, "", &stat, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW); if (res == -1) { fuse_log(FUSE_LOG_ERR, "fstatat(%s): %m\n", lo->source); exit(1); } root->filetype = S_IFDIR; root->fd = fd; root->key.ino = stat.st_ino; root->key.dev = stat.st_dev; root->nlookup = 2; g_atomic_int_set(&root->refcount, 2); } static guint lo_key_hash(gconstpointer key) { const struct lo_key *lkey = key; return (guint)lkey->ino + (guint)lkey->dev; } static gboolean lo_key_equal(gconstpointer a, gconstpointer b) { const struct lo_key *la = a; const struct lo_key *lb = b; return la->ino == lb->ino && la->dev == lb->dev; } static void fuse_lo_data_cleanup(struct lo_data *lo) { if (lo->inodes) { g_hash_table_destroy(lo->inodes); } lo_map_destroy(&lo->fd_map); lo_map_destroy(&lo->dirp_map); lo_map_destroy(&lo->ino_map); if (lo->proc_self_fd >= 0) { close(lo->proc_self_fd); } if (lo->root.fd >= 0) { close(lo->root.fd); } free(lo->source); } int main(int argc, char *argv[]) { struct fuse_args args = FUSE_ARGS_INIT(argc, argv); struct fuse_session *se; struct fuse_cmdline_opts opts; struct lo_data lo = { .debug = 0, .writeback = 0, .posix_lock = 0, .allow_direct_io = 0, .proc_self_fd = -1, }; struct lo_map_elem *root_elem; int ret = -1; /* Don't mask creation mode, kernel already did that */ umask(0); pthread_mutex_init(&lo.mutex, NULL); lo.inodes = g_hash_table_new(lo_key_hash, lo_key_equal); lo.root.fd = -1; lo.root.fuse_ino = FUSE_ROOT_ID; lo.cache = CACHE_AUTO; /* * Set up the ino map like this: * [0] Reserved (will not be used) * [1] Root inode */ lo_map_init(&lo.ino_map); lo_map_reserve(&lo.ino_map, 0)->in_use = false; root_elem = lo_map_reserve(&lo.ino_map, lo.root.fuse_ino); root_elem->inode = &lo.root; lo_map_init(&lo.dirp_map); lo_map_init(&lo.fd_map); if (fuse_parse_cmdline(&args, &opts) != 0) { goto err_out1; } fuse_set_log_func(log_func); use_syslog = opts.syslog; if (use_syslog) { openlog("virtiofsd", LOG_PID, LOG_DAEMON); } if (opts.show_help) { printf("usage: %s [options]\n\n", argv[0]); fuse_cmdline_help(); printf(" -o source=PATH shared directory tree\n"); fuse_lowlevel_help(); ret = 0; goto err_out1; } else if (opts.show_version) { fuse_lowlevel_version(); ret = 0; goto err_out1; } else if (opts.print_capabilities) { print_capabilities(); ret = 0; goto err_out1; } if (fuse_opt_parse(&args, &lo, lo_opts, NULL) == -1) { goto err_out1; } /* * log_level is 0 if not configured via cmd options (0 is LOG_EMERG, * and we don't use this log level). */ if (opts.log_level != 0) { current_log_level = opts.log_level; } lo.debug = opts.debug; if (lo.debug) { current_log_level = FUSE_LOG_DEBUG; } if (lo.source) { struct stat stat; int res; res = lstat(lo.source, &stat); if (res == -1) { fuse_log(FUSE_LOG_ERR, "failed to stat source (\"%s\"): %m\n", lo.source); exit(1); } if (!S_ISDIR(stat.st_mode)) { fuse_log(FUSE_LOG_ERR, "source is not a directory\n"); exit(1); } } else { lo.source = strdup("/"); } if (!lo.timeout_set) { switch (lo.cache) { case CACHE_NONE: lo.timeout = 0.0; break; case CACHE_AUTO: lo.timeout = 1.0; break; case CACHE_ALWAYS: lo.timeout = 86400.0; break; } } else if (lo.timeout < 0) { fuse_log(FUSE_LOG_ERR, "timeout is negative (%lf)\n", lo.timeout); exit(1); } se = fuse_session_new(&args, &lo_oper, sizeof(lo_oper), &lo); if (se == NULL) { goto err_out1; } if (fuse_set_signal_handlers(se) != 0) { goto err_out2; } if (fuse_session_mount(se) != 0) { goto err_out3; } fuse_daemonize(opts.foreground); setup_nofile_rlimit(opts.rlimit_nofile); /* Must be before sandbox since it wants /proc */ setup_capng(); setup_sandbox(&lo, se, opts.syslog); setup_root(&lo, &lo.root); /* Block until ctrl+c or fusermount -u */ ret = virtio_loop(se); fuse_session_unmount(se); cleanup_capng(); err_out3: fuse_remove_signal_handlers(se); err_out2: fuse_session_destroy(se); err_out1: fuse_opt_free_args(&args); fuse_lo_data_cleanup(&lo); return ret ? 1 : 0; }