Commit 4ecd55ea authored Nov 28, 2018 by Vasily Averin Committed by J. Bruce Fields Dec 04, 2018

sunrpc: fix cache_head leak due to queued request



After commit d202cce8, an expired cache_head can be removed from the
cache_detail's hash.

However, the expired cache_head may be waiting for a reply from a
previously submitted request. Such a cache_head has an increased
refcounter and therefore it won't be freed after cache_put(freeme).

Because the cache_head was removed from the hash it cannot be found
during cache_clean() and can be leaked forever, together with stalled
cache_request and other taken resources.

In our case we noticed it because an entry in the export cache was
holding a reference on a filesystem.

Fixes d202cce8 ("sunrpc: never return expired entries in sunrpc_cache_lookup")
Cc: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Cc: stable@kernel.org # 2.6.35
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

parent f50c9d79

net/sunrpc/cache.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -54,6 +54,11 @@ static void cache_init(struct cache_head h, struct cache_detail detail)
		h->last_refresh = now;
		}

		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,
		struct cache_detail *detail);

		static struct cache_head sunrpc_cache_find_rcu(struct cache_detail detail,
		struct cache_head *key,
		int hash)
		@@ -100,6 +105,7 @@ static struct cache_head sunrpc_cache_add_entry(struct cache_detail detail,
		if (cache_is_expired(detail, tmp)) {
		hlist_del_init_rcu(&tmp->cache_list);
		detail->entries --;
		cache_fresh_locked(tmp, 0, detail);
		freeme = tmp;
		break;
		}
		@@ -115,8 +121,10 @@ static struct cache_head sunrpc_cache_add_entry(struct cache_detail detail,
		cache_get(new);
		spin_unlock(&detail->hash_lock);

		if (freeme)
		if (freeme) {
		cache_fresh_unlocked(freeme, detail);
		cache_put(freeme, detail);
		}
		return new;
		}

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