diff options
| author | Greg Kurz <groug@kaod.org> | 2018-11-07 01:00:04 +0100 |
|---|---|---|
| committer | Greg Kurz <groug@kaod.org> | 2018-11-08 21:19:05 +0100 |
| commit | 5b76ef50f62079a2389ba28cacaf6cce68b1a0ed (patch) | |
| tree | 96d84008da66d9464e1799b7af71fa13111fa6e2 | |
| parent | a7ce790a029bd94eb320d8c69f38900f5233997e (diff) | |
9p: write lock path in v9fs_co_open2()
The assumption that the fid cannot be used by any other operation is
wrong. At least, nothing prevents a misbehaving client to create a
file with a given fid, and to pass this fid to some other operation
at the same time (ie, without waiting for the response to the creation
request). The call to v9fs_path_copy() performed by the worker thread
after the file was created can race with any access to the fid path
performed by some other thread. This causes use-after-free issues that
can be detected by ASAN with a custom 9p client.
Unlike other operations that only read the fid path, v9fs_co_open2()
does modify it. It should hence take the write lock.
Cc: P J P <ppandit@redhat.com>
Reported-by: zhibin hu <noirfate@gmail.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
| -rw-r--r-- | hw/9pfs/cofile.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/hw/9pfs/cofile.c b/hw/9pfs/cofile.c index 88791bc327..9c22837cda 100644 --- a/hw/9pfs/cofile.c +++ b/hw/9pfs/cofile.c @@ -140,10 +140,10 @@ int coroutine_fn v9fs_co_open2(V9fsPDU *pdu, V9fsFidState *fidp, cred.fc_gid = gid; /* * Hold the directory fid lock so that directory path name - * don't change. Read lock is fine because this fid cannot - * be used by any other operation. + * don't change. Take the write lock to be sure this fid + * cannot be used by another operation. */ - v9fs_path_read_lock(s); + v9fs_path_write_lock(s); v9fs_co_run_in_worker( { err = s->ops->open2(&s->ctx, &fidp->path, |