nfsd: only unhash DRC entries that are in the hashtable

It's not safe to call hlist_del() on a newly initialized hlist_node.
That leads to a NULL pointer dereference. Only do that if the entry
is hashed.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 62c1ee128aeb..18509bd6f587 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -102,7 +102,8 @@ nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
 {
         if (rp->c_type == RC_REPLBUFF)
                 kfree(rp->c_replvec.iov_base);
-        hlist_del(&rp->c_hash);
+        if (!hlist_unhashed(&rp->c_hash))
+                hlist_del(&rp->c_hash);
         list_del(&rp->c_lru);
         --num_drc_entries;
         kmem_cache_free(drc_slab, rp);