linux-kernel - Re: snd_seq_timer_open() NULL pointer dereference

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Date:	Fri, 08 Mar 2013 18:31:20 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Tommi Rantala <tt.rantala@...il.com>
Cc:	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: snd_seq_timer_open() NULL pointer dereference

At Thu, 7 Mar 2013 21:59:32 +0200,
Tommi Rantala wrote:
> 
> Hello,
> 
> I'm hitting this while fuzzing the kernel with Trinity:

The patch below fixes a clear bug in the code path.
Could you check whether it'll fit?


thanks,

Takashi

---
From: Takashi Iwai <tiwai@...e.de>
Subject: [PATCH] ALSA: seq: Fix missing error handling in snd_seq_timer_open()

snd_seq_timer_open() didn't catch the whole error path but let through
if the timer id is a slave.  This may lead to Oops by accessing the
uninitialized pointer.

Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 sound/core/seq/seq_timer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c
index 160b1bd..24d44b2 100644
--- a/sound/core/seq/seq_timer.c
+++ b/sound/core/seq/seq_timer.c
@@ -290,10 +290,10 @@ int snd_seq_timer_open(struct snd_seq_queue *q)
 			tid.device = SNDRV_TIMER_GLOBAL_SYSTEM;
 			err = snd_timer_open(&t, str, &tid, q->queue);
 		}
-		if (err < 0) {
-			snd_printk(KERN_ERR "seq fatal error: cannot create timer (%i)\n", err);
-			return err;
-		}
+	}
+	if (err < 0) {
+		snd_printk(KERN_ERR "seq fatal error: cannot create timer (%i)\n", err);
+		return err;
 	}
 	t->callback = snd_seq_timer_interrupt;
 	t->callback_data = q;
-- 
1.8.1.4

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