hw/9pfs: use g_strdup_printf() instead of PATH_MAX limitation

When path is truncated by PATH_MAX limitation, it causes QEMU to access
incorrect file. So use original full path instead of PATH_MAX within
9pfs (need check/process ENOMEM for related memory allocation).

The related test:

 - Environments (for qemu-devel):

   - Host is under fedora17 desktop with ext4fs:

     qemu-system-x86_64 -hda test.img -m 1024 \
       -net nic,vlan=4,model=virtio,macaddr=00:16:35:AF:94:04 \
       -net tap,vlan=4,ifname=tap4,script=no,downscript=no \
       -device virtio-9p-pci,id=fs0,fsdev=fsdev0,mount_tag=hostshare \
       -fsdev local,security_model=passthrough,id=fsdev0,\
         path=/upstream/vm/data/share/1234567890abcdefghijklmnopqrstuvwxyz\
           ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890acdefghijklmnopqrstuvwxyz\
           ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890/111111111111111111111111111\
           1111111111111111111111111111111111111111111111111111222222222222\
           2222222222222222222222222222222222222222222222222222222222222222\
           2222222222222222222222222222222222233333333333333333333333333333\
           3333333333333333333333333333333333

    - Guest is ubuntu12 server with 9pfs.

      mount -t 9p -o trans=virtio,version=9p2000.L hostshare /share

    - Limitations:

      full path limitation is PATH_MAX (4096B include nul) under Linux.
      file/dir node name maximized length is 256 (include nul) under ext4.

 - Special test:

    Under host, modify the file: "/upstream/vm/data/share/1234567890abcdefg\
      hijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890acdefghijklmno\
      pqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890/111111111111111111111\
      111111111111111111111111111111111111111111111111111111111122222222222\
      222222222222222222222222222222222222222222222222222222222222222222222\
      222222222222222222222222222222233333333333333333333333333333333333333\
      3333333333333333333333333/4444444444444444444444444444444444444444444\
      444444444444444444444444444444444444444444444444444444444444444444444\
      444444444444444444444444444444444444444444444444444444444444444444444\
      444444444444444444444444444444444444444/55555555555555555555555555555\
      555555555555555555555555555555555555555555555555555555555555555555555\
      555555555555555555555555555555555555555555555555555555555555555555555\
      555555555555555555555555555555555555555555555555555555555555555555555\
      55555555/666666666666666666666666666666666666666666666666666666666666\
      666666666666666666666666666666666666666666666666666666666666666666666\
      666666666666666666666666666666666666666666666666666666666666666666666\
      666666666666666666666/77777777777777777777777777777777777777777777777\
      777777777777777777777777777777777777777777777777777777777777777777777\
      777777777777777777777777777777777777777777777777777777777777777777777\
      77777777777777777777777777777777777777777777777777777777777/888888888\
      888888888888888888888888888888888888888888888888888888888888888888888\
      888888888888888888888888888888888888888888888888888888888888888888888\
      888888888888888888888888888888888888888888888888888888888888888888888\
      888888888/99999999999999999999999999999999999999999999999999999999999\
      999999999999999999999999999999999999999999999999999999999999999999999\
      999999999999999999999999999999999999999999999999999999999999999999999\
      99999999999999999999999999999999999999999/000000000000000000000000000\
      000000000000000000000000000000000000000000000000000000000000000000000\
      000000000000000000000000000000000000000000000000000000000000000000000\
      000000000000000000000000000000000000000000000000/aaaaaaaaaaaaaaaaaaaa\
      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\
      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbb\
      bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\
      bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\
      bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/ccccccccc\
      ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc\
      ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc\
      ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc\
      cccccccccc/dddddddddddddddddddddddddddddddddddddddddddddddddddddddddd\
      ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd\
      ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd\
      dddddddddddddddddddddd/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee\
      eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee\
      eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee\
      eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee/fffffffffffffff\
      fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff\
      fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff\
      ffffffffffffffffffffffffffffffffffffffffffffffffffffffffff/gggggggggg\
      ggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg\
      ggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg\
      ggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg\
      ggggggggggggggggggggggg/iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii\
      iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii\
      iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii\
      iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii/jjjjjjjjjjjjj\
      jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj\
      jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj/ppppppppppppppppppppp\
      ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp\
      ppppppppppppppppppppppppppppppppppppppp/test1234567890file.log"
        (need enter dir firstly, then modify file, or can not open it).

   Under guest, still allow modify "test1234567890file.log" (will generate
   "test123456" file with contents).

   After apply this patch, can not open "test1234567890file.log" under guest
   (permission denied).

 - Common test:

   All are still OK after apply this path.

     "mkdir -p", "create/open file/dir", "modify file/dir", "rm file/dir".
     change various mount point paths under host and/or guest.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

1 files changed, 38 insertions, 14 deletions

diff --git a/hw/9pfs/virtio-9p-posix-acl.c b/hw/9pfs/virtio-9p-posix-acl.c
index 339c5ecae4..803d9d94f3 100644
--- a/hw/9pfs/virtio-9p-posix-acl.c
+++ b/hw/9pfs/virtio-9p-posix-acl.c
@@ -26,8 +26,13 @@
 static ssize_t mp_pacl_getxattr(FsContext *ctx, const char *path,
                                 const char *name, void *value, size_t size)
 {
-    char buffer[PATH_MAX];
-    return lgetxattr(rpath(ctx, path, buffer), MAP_ACL_ACCESS, value, size);
+    char *buffer;
+    ssize_t ret;
+
+    buffer = rpath(ctx, path);
+    ret = lgetxattr(buffer, MAP_ACL_ACCESS, value, size);
+    g_free(buffer);
+    return ret;
 }
 
 static ssize_t mp_pacl_listxattr(FsContext *ctx, const char *path,
@@ -52,17 +57,23 @@ static ssize_t mp_pacl_listxattr(FsContext *ctx, const char *path,
 static int mp_pacl_setxattr(FsContext *ctx, const char *path, const char *name,
                             void *value, size_t size, int flags)
 {
-    char buffer[PATH_MAX];
-    return lsetxattr(rpath(ctx, path, buffer), MAP_ACL_ACCESS, value,
-            size, flags);
+    char *buffer;
+    int ret;
+
+    buffer = rpath(ctx, path);
+    ret = lsetxattr(buffer, MAP_ACL_ACCESS, value, size, flags);
+    g_free(buffer);
+    return ret;
 }
 
 static int mp_pacl_removexattr(FsContext *ctx,
                                const char *path, const char *name)
 {
     int ret;
-    char buffer[PATH_MAX];
-    ret  = lremovexattr(rpath(ctx, path, buffer), MAP_ACL_ACCESS);
+    char *buffer;
+
+    buffer = rpath(ctx, path);
+    ret  = lremovexattr(buffer, MAP_ACL_ACCESS);
     if (ret == -1 && errno == ENODATA) {
         /*
          * We don't get ENODATA error when trying to remove a
@@ -72,14 +83,20 @@ static int mp_pacl_removexattr(FsContext *ctx,
         errno = 0;
         ret = 0;
     }
+    g_free(buffer);
     return ret;
 }
 
 static ssize_t mp_dacl_getxattr(FsContext *ctx, const char *path,
                                 const char *name, void *value, size_t size)
 {
-    char buffer[PATH_MAX];
-    return lgetxattr(rpath(ctx, path, buffer), MAP_ACL_DEFAULT, value, size);
+    char *buffer;
+    ssize_t ret;
+
+    buffer = rpath(ctx, path);
+    ret = lgetxattr(buffer, MAP_ACL_DEFAULT, value, size);
+    g_free(buffer);
+    return ret;
 }
 
 static ssize_t mp_dacl_listxattr(FsContext *ctx, const char *path,
@@ -104,17 +121,23 @@ static ssize_t mp_dacl_listxattr(FsContext *ctx, const char *path,
 static int mp_dacl_setxattr(FsContext *ctx, const char *path, const char *name,
                             void *value, size_t size, int flags)
 {
-    char buffer[PATH_MAX];
-    return lsetxattr(rpath(ctx, path, buffer), MAP_ACL_DEFAULT, value,
-            size, flags);
+    char *buffer;
+    int ret;
+
+    buffer = rpath(ctx, path);
+    ret = lsetxattr(buffer, MAP_ACL_DEFAULT, value, size, flags);
+    g_free(buffer);
+    return ret;
 }
 
 static int mp_dacl_removexattr(FsContext *ctx,
                                const char *path, const char *name)
 {
     int ret;
-    char buffer[PATH_MAX];
-    ret  = lremovexattr(rpath(ctx, path, buffer), MAP_ACL_DEFAULT);
+    char *buffer;
+
+    buffer = rpath(ctx, path);
+    ret  = lremovexattr(buffer, MAP_ACL_DEFAULT);
     if (ret == -1 && errno == ENODATA) {
         /*
          * We don't get ENODATA error when trying to remove a
@@ -124,6 +147,7 @@ static int mp_dacl_removexattr(FsContext *ctx,
         errno = 0;
         ret = 0;
     }
+    g_free(buffer);
     return ret;
 }