Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946402AbbEPIEw (ORCPT ); Sat, 16 May 2015 04:04:52 -0400 Received: from bband-dyn183.178-41-215.t-com.sk ([178.41.215.183]:22442 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1946382AbbEPIEp (ORCPT ); Sat, 16 May 2015 04:04:45 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Alexey Khoroshilov , Takashi Iwai , Willy Tarreau , Jiri Slaby Subject: [PATCH 3.12 138/142] sound/oss: fix deadlock in sequencer_ioctl(SNDCTL_SEQ_OUTOFBAND) Date: Sat, 16 May 2015 09:38:18 +0200 Message-Id: <37db8fd4ace9131edd8659e8a69fefb327b1790d.1431761807.git.jslaby@suse.cz> X-Mailer: git-send-email 2.3.7 In-Reply-To: <70c3d4ae1322b9e9bd7443ef574af5635234a0fa.1431761807.git.jslaby@suse.cz> References: <70c3d4ae1322b9e9bd7443ef574af5635234a0fa.1431761807.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2880 Lines: 91 From: Alexey Khoroshilov 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit bc26d4d06e337ade069f33d3f4377593b24e6e36 upstream. A deadlock can be initiated by userspace via ioctl(SNDCTL_SEQ_OUTOFBAND) on /dev/sequencer with TMR_ECHO midi event. In this case the control flow is: sound_ioctl() -> case SND_DEV_SEQ: case SND_DEV_SEQ2: sequencer_ioctl() -> case SNDCTL_SEQ_OUTOFBAND: spin_lock_irqsave(&lock,flags); play_event(); -> case EV_TIMING: seq_timing_event() -> case TMR_ECHO: seq_copy_to_input() -> spin_lock_irqsave(&lock,flags); It seems that spin_lock_irqsave() around play_event() is not necessary, because the only other call location in seq_startplay() makes the call without acquiring spinlock. So, the patch just removes spinlocks around play_event(). By the way, it removes unreachable code in seq_timing_event(), since (seq_mode == SEQ_2) case is handled in the beginning. Compile tested only. Found by Linux Driver Verification project (linuxtesting.org). Signed-off-by: Alexey Khoroshilov Signed-off-by: Takashi Iwai Cc: Willy Tarreau Signed-off-by: Jiri Slaby --- sound/oss/sequencer.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/sound/oss/sequencer.c b/sound/oss/sequencer.c index 4ff60a6427d9..2e67dd590be5 100644 --- a/sound/oss/sequencer.c +++ b/sound/oss/sequencer.c @@ -683,13 +683,8 @@ static int seq_timing_event(unsigned char *event_rec) break; case TMR_ECHO: - if (seq_mode == SEQ_2) - seq_copy_to_input(event_rec, 8); - else - { - parm = (parm << 8 | SEQ_ECHO); - seq_copy_to_input((unsigned char *) &parm, 4); - } + parm = (parm << 8 | SEQ_ECHO); + seq_copy_to_input((unsigned char *) &parm, 4); break; default:; @@ -1332,7 +1327,6 @@ int sequencer_ioctl(int dev, struct file *file, unsigned int cmd, void __user *a int mode = translate_mode(file); struct synth_info inf; struct seq_event_rec event_rec; - unsigned long flags; int __user *p = arg; orig_dev = dev = dev >> 4; @@ -1487,9 +1481,7 @@ int sequencer_ioctl(int dev, struct file *file, unsigned int cmd, void __user *a case SNDCTL_SEQ_OUTOFBAND: if (copy_from_user(&event_rec, arg, sizeof(event_rec))) return -EFAULT; - spin_lock_irqsave(&lock,flags); play_event(event_rec.arr); - spin_unlock_irqrestore(&lock,flags); return 0; case SNDCTL_MIDI_INFO: -- 2.3.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/