Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753836AbcD0AcT (ORCPT ); Tue, 26 Apr 2016 20:32:19 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:39822 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753742AbcDZXNk (ORCPT ); Tue, 26 Apr 2016 19:13:40 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "J. Bruce Fields" , "NeilBrown" Date: Wed, 27 Apr 2016 01:02:21 +0200 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 117/217] sunrpc/cache: drop reference when sunrpc_cache_pipe_upcall() detects a race In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8426:ae4:c500:9cba:69ae:962d:6167 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1364 Lines: 43 3.16.35-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: NeilBrown commit a6ab1e8126d205238defbb55d23661a3a5c6a0d8 upstream. sunrpc_cache_pipe_upcall() can detect a race if CACHE_PENDING is no longer set. In this case it aborts the queuing of the upcall. However it has already taken a new counted reference on "h" and doesn't "put" it, even though it frees the data structure holding the reference. So let's delay the "cache_get" until we know we need it. Fixes: f9e1aedc6c79 ("sunrpc/cache: remove races with queuing an upcall.") Signed-off-by: NeilBrown Signed-off-by: J. Bruce Fields Signed-off-by: Ben Hutchings --- net/sunrpc/cache.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -1187,14 +1187,14 @@ int sunrpc_cache_pipe_upcall(struct cach } crq->q.reader = 0; - crq->item = cache_get(h); crq->buf = buf; crq->len = 0; crq->readers = 0; spin_lock(&queue_lock); - if (test_bit(CACHE_PENDING, &h->flags)) + if (test_bit(CACHE_PENDING, &h->flags)) { + crq->item = cache_get(h); list_add_tail(&crq->q.list, &detail->queue); - else + } else /* Lost a race, no longer PENDING, so don't enqueue */ ret = -EAGAIN; spin_unlock(&queue_lock);