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authorNeilBrown <neilb@suse.com>2019-03-19 11:33:24 +1100
committerTrond Myklebust <trond.myklebust@hammerspace.com>2019-03-18 22:39:34 -0400
commit4a9be28c45bf02fa0436808bb6c0baeba30e120e (patch)
tree281d3195bf4c2743e76911099151d874930b8621
parent3028efe03be9c8c4cd7923f0f3c39b2871cc8a8f (diff)
downloadlinux-4a9be28c45bf02fa0436808bb6c0baeba30e120e.tar.bz2
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.c3
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);
}