From: NeilBrown neilb@suse.com
commit d58431eacb226222430940134d97bfd72f292fcd upstream.
A recent commit added a call to cache_fresh_locked() when an expired item was found. The call sets the CACHE_VALID flag, so it is important that the item actually is valid. There are two ways it could be valid: 1/ If ->update has been called to fill in relevant content 2/ if CACHE_NEGATIVE is set, to say that content doesn't exist.
An expired item that is waiting for an update will be neither. Setting CACHE_VALID will mean that a subsequent call to cache_put() will be likely to dereference uninitialised pointers.
So we must make sure the item is valid, and we already have code to do that in try_to_negate_entry(). This takes the hash lock and so cannot be used directly, so take out the two lines that we need and use them.
Now cache_fresh_locked() is certain to be called only on a valid item.
Cc: stable@kernel.org # 2.6.35 Fixes: 4ecd55ea0742 ("sunrpc: fix cache_head leak due to queued request") Signed-off-by: NeilBrown neilb@suse.com Signed-off-by: J. Bruce Fields bfields@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/sunrpc/cache.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -54,6 +54,7 @@ static void cache_init(struct cache_head h->last_refresh = now; }
+static inline int cache_is_valid(struct cache_head *h); static void cache_fresh_locked(struct cache_head *head, time_t expiry, struct cache_detail *detail); static void cache_fresh_unlocked(struct cache_head *head, @@ -105,6 +106,8 @@ static struct cache_head *sunrpc_cache_a if (cache_is_expired(detail, tmp)) { hlist_del_init_rcu(&tmp->cache_list); detail->entries --; + if (cache_is_valid(tmp) == -EAGAIN) + set_bit(CACHE_NEGATIVE, &tmp->flags); cache_fresh_locked(tmp, 0, detail); freeme = tmp; break;