Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:35898 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031186AbeGAQf5 (ORCPT ); Sun, 1 Jul 2018 12:35:57 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Takashi Iwai Subject: [PATCH 4.14 147/157] ALSA: timer: Fix UBSAN warning at SNDRV_TIMER_IOCTL_NEXT_DEVICE ioctl Date: Sun, 1 Jul 2018 18:23:39 +0200 Message-Id: <20180701160900.522711854@linuxfoundation.org> In-Reply-To: <20180701160852.287307684@linuxfoundation.org> References: <20180701160852.287307684@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit b41f794f284966fd6ec634111e3b40d241389f96 upstream. The kernel may spew a WARNING about UBSAN undefined behavior at handling ALSA timer ioctl SNDRV_TIMER_IOCTL_NEXT_DEVICE: UBSAN: Undefined behaviour in sound/core/timer.c:1524:19 signed integer overflow: 2147483647 + 1 cannot be represented in type 'int' Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x122/0x1c8 lib/dump_stack.c:113 ubsan_epilogue+0x12/0x86 lib/ubsan.c:159 handle_overflow+0x1c2/0x21f lib/ubsan.c:190 __ubsan_handle_add_overflow+0x2a/0x31 lib/ubsan.c:198 snd_timer_user_next_device sound/core/timer.c:1524 [inline] __snd_timer_user_ioctl+0x204d/0x2520 sound/core/timer.c:1939 snd_timer_user_ioctl+0x67/0x95 sound/core/timer.c:1994 .... It happens only when a value with INT_MAX is passed, as we're incrementing it unconditionally. So the fix is trivial, check the value with INT_MAX. Although the bug itself is fairly harmless, it's better to fix it so that fuzzers won't hit this again later. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200213 Reported-and-tested-by: Team OWL337 Cc: Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1514,7 +1514,7 @@ static int snd_timer_user_next_device(st } else { if (id.subdevice < 0) id.subdevice = 0; - else + else if (id.subdevice < INT_MAX) id.subdevice++; } }