diff options
| author | J. Bruce Fields <bfields@redhat.com> | 2019-04-12 16:37:30 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-06-22 08:17:15 +0200 |
| commit | 101e808f7e75da2e0e9fb5aefc2bc3c92209eacd (patch) | |
| tree | b3fd7b48a8c752dfa06ac4fdac8f1ca978481387 /fs/nfsd | |
| parent | 4edf907dcd42d1d5790b54db472d08ee67c348a2 (diff) | |
nfsd: allow fh_want_write to be called twice
[ Upstream commit 0b8f62625dc309651d0efcb6a6247c933acd8b45 ]
A fuzzer recently triggered lockdep warnings about potential sb_writers
deadlocks caused by fh_want_write().
Looks like we aren't careful to pair each fh_want_write() with an
fh_drop_write().
It's not normally a problem since fh_put() will call fh_drop_write() for
us. And was OK for NFSv3 where we'd do one operation that might call
fh_want_write(), and then put the filehandle.
But an NFSv4 protocol fuzzer can do weird things like call unlink twice
in a compound, and then we get into trouble.
I'm a little worried about this approach of just leaving everything to
fh_put(). But I think there are probably a lot of
fh_want_write()/fh_drop_write() imbalances so for now I think we need it
to be more forgiving.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'fs/nfsd')
| -rw-r--r-- | fs/nfsd/vfs.h | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h index 0bf9e7bf5800..9140b9cf3870 100644 --- a/fs/nfsd/vfs.h +++ b/fs/nfsd/vfs.h @@ -116,8 +116,11 @@ void nfsd_put_raparams(struct file *file, struct raparms *ra); static inline int fh_want_write(struct svc_fh *fh) { - int ret = mnt_want_write(fh->fh_export->ex_path.mnt); + int ret; + if (fh->fh_want_write) + return 0; + ret = mnt_want_write(fh->fh_export->ex_path.mnt); if (!ret) fh->fh_want_write = true; return ret; |