Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756880AbcDDX3a (ORCPT ); Mon, 4 Apr 2016 19:29:30 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35380 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756851AbcDDX30 (ORCPT ); Mon, 4 Apr 2016 19:29:26 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: NeilBrown , "J . Bruce Fields" , Kamal Mostafa Subject: [PATCH 3.13.y-ckt 87/97] sunrpc/cache: drop reference when sunrpc_cache_pipe_upcall() detects a race Date: Mon, 4 Apr 2016 16:26:51 -0700 Message-Id: <1459812421-933-88-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1459812421-933-1-git-send-email-kamal@canonical.com> References: <1459812421-933-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1553 Lines: 47 3.13.11-ckt38 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ 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: Kamal Mostafa --- net/sunrpc/cache.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index f3e2b7d..b81e0a3 100644 --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -1189,14 +1189,14 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h) } 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); -- 2.7.4