diff options
| author | NeilBrown <neilb@suse.com> | 2019-03-19 11:33:24 +1100 |
|---|---|---|
| committer | Trond Myklebust <trond.myklebust@hammerspace.com> | 2019-03-18 22:39:34 -0400 |
| commit | 4a9be28c45bf02fa0436808bb6c0baeba30e120e (patch) | |
| tree | 281d3195bf4c2743e76911099151d874930b8621 | |
| parent | 3028efe03be9c8c4cd7923f0f3c39b2871cc8a8f (diff) | |
NFS: fix mount/umount race in nlmclnt.
If the last NFSv3 unmount from a given host races with a mount from the
same host, we can destroy an nlm_host that is still in use.
Specifically nlmclnt_lookup_host() can increment h_count on
an nlm_host that nlmclnt_release_host() has just successfully called
refcount_dec_and_test() on.
Once nlmclnt_lookup_host() drops the mutex, nlm_destroy_host_lock()
will be called to destroy the nlmclnt which is now in use again.
The cause of the problem is that the dec_and_test happens outside the
locked region. This is easily fixed by using
refcount_dec_and_mutex_lock().
Fixes: 8ea6ecc8b075 ("lockd: Create client-side nlm_host cache")
Cc: stable@vger.kernel.org (v2.6.38+)
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
| -rw-r--r-- | fs/lockd/host.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/fs/lockd/host.c b/fs/lockd/host.c index 93fb7cf0b92b..f0b5c987d6ae 100644 --- a/fs/lockd/host.c +++ b/fs/lockd/host.c @@ -290,12 +290,11 @@ void nlmclnt_release_host(struct nlm_host *host) WARN_ON_ONCE(host->h_server); - if (refcount_dec_and_test(&host->h_count)) { + if (refcount_dec_and_mutex_lock(&host->h_count, &nlm_host_mutex)) { WARN_ON_ONCE(!list_empty(&host->h_lockowners)); WARN_ON_ONCE(!list_empty(&host->h_granted)); WARN_ON_ONCE(!list_empty(&host->h_reclaim)); - mutex_lock(&nlm_host_mutex); nlm_destroy_host_locked(host); mutex_unlock(&nlm_host_mutex); } |