Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754456AbdFSSk5 (ORCPT + 2 others); Mon, 19 Jun 2017 14:40:57 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:52798 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754443AbdFSSky (ORCPT ); Mon, 19 Jun 2017 14:40:54 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Takashi Iwai , Willy Tarreau Subject: [PATCH 3.10 041/268] ALSA: seq: Fix race during FIFO resize Date: Mon, 19 Jun 2017 20:29:00 +0200 Message-Id: <1497897167-14556-42-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1497897167-14556-1-git-send-email-w@1wt.eu> References: <1497897167-14556-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Takashi Iwai commit 2d7d54002e396c180db0c800c1046f0a3c471597 upstream. When a new event is queued while processing to resize the FIFO in snd_seq_fifo_clear(), it may lead to a use-after-free, as the old pool that is being queued gets removed. For avoiding this race, we need to close the pool to be deleted and sync its usage before actually deleting it. The issue was spotted by syzkaller. Reported-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Willy Tarreau --- sound/core/seq/seq_fifo.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/sound/core/seq/seq_fifo.c b/sound/core/seq/seq_fifo.c index fc2c55b..490b697 100644 --- a/sound/core/seq/seq_fifo.c +++ b/sound/core/seq/seq_fifo.c @@ -267,6 +267,10 @@ int snd_seq_fifo_resize(struct snd_seq_fifo *f, int poolsize) /* NOTE: overflow flag is not cleared */ spin_unlock_irqrestore(&f->lock, flags); + /* close the old pool and wait until all users are gone */ + snd_seq_pool_mark_closing(oldpool); + snd_use_lock_sync(&f->use_lock); + /* release cells in old pool */ for (cell = oldhead; cell; cell = next) { next = cell->next; -- 2.8.0.rc2.1.gbe9624a