linux-kernel - Re: [PATCH] [media] sound/usb: fix NULL dereference in usb_audio

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Message-ID: <20160315115339.2a50466a@recife.lan>
Date:	Tue, 15 Mar 2016 11:53:39 -0300
From:	Mauro Carvalho Chehab <mchehab@....samsung.com>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Nicolai Stange <nicstange@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	Shuah Khan <shuahkh@....samsung.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [media] sound/usb: fix NULL dereference in
 usb_audio_probe()

Em Tue, 15 Mar 2016 13:41:28 +0100
Takashi Iwai <tiwai@...e.de> escreveu:

> On Tue, 15 Mar 2016 13:35:06 +0100,
> Nicolai Stange wrote:
> > 
> > With commit
> > 
> >   aebb2b89bff0 ("[media] sound/usb: Use Media Controller API to share
> >                  media resources")
> > 
> > an access to quirk->media_device without checking for quirk != NULL has
> > been introduced in usb_audio_probe().
> > 
> > With a Plantronics USB headset (device ID 0x047f:0xc010) attached,
> > this results in the following splat at boot time:
> > 
> >   BUG: unable to handle kernel NULL pointer dereference at 0000000000000014
> >   IP: [<ffffffffa089aa6c>] usb_audio_probe+0x2cc/0x9a0 [snd_usb_audio]
> >   Oops: 0000 [#1] SMP
> >   [...]
> >   CPU: 2 PID: 696 Comm: systemd-udevd Not tainted 4.5.0-next-20160315 #13
> >   Hardware name: Dell Inc. Latitude E6540/0725FP, BIOS A10 06/26/2014
> >   task: ffff88021c88d7c0 ti: ffff88003d5b0000 task.ti: ffff88003d5b0000
> >   RIP: 0010:[<ffffffffa089aa6c>]  [<ffffffffa089aa6c>]
> >                                 usb_audio_probe+0x2cc/0x9a0 [snd_usb_audio]
> >   [...]
> >   Call Trace:
> >    [<ffffffff815a8e16>] usb_probe_interface+0x136/0x2d0
> >    [<ffffffff81509edc>] driver_probe_device+0x22c/0x440
> >    [<ffffffff8150a1c1>] __driver_attach+0xd1/0xf0
> >    [<ffffffff8150a0f0>] ? driver_probe_device+0x440/0x440
> >    [<ffffffff815077ec>] bus_for_each_dev+0x6c/0xc0
> >    [<ffffffff815095ce>] driver_attach+0x1e/0x20
> >    [<ffffffff81509013>] bus_add_driver+0x1c3/0x280
> >    [<ffffffff8150ab10>] driver_register+0x60/0xe0
> >    [<ffffffff815a7711>] usb_register_driver+0x81/0x140
> >    [<ffffffffa08c7000>] ? 0xffffffffa08c7000
> >    [<ffffffffa08c701e>] usb_audio_driver_init+0x1e/0x1000 [snd_usb_audio]
> >    [<ffffffff81002123>] do_one_initcall+0xb3/0x1f0
> >    [<ffffffff811fb091>] ? __vunmap+0x81/0xd0
> >    [<ffffffff8121b8d2>] ? kmem_cache_alloc_trace+0x182/0x1d0
> >    [<ffffffff811b0267>] ? do_init_module+0x27/0x1d8
> >    [<ffffffff811b029f>] do_init_module+0x5f/0x1d8
> >    [<ffffffff8112ce35>] load_module+0x1fe5/0x27a0
> >    [<ffffffff81129870>] ? __symbol_put+0x60/0x60
> >    [<ffffffff81241690>] ? vfs_read+0x110/0x130
> >    [<ffffffff8112d866>] SYSC_finit_module+0xe6/0x120
> >    [<ffffffff8112d8be>] SyS_finit_module+0xe/0x10
> >    [<ffffffff81003d94>] do_syscall_64+0x64/0x110
> >    [<ffffffff817c0b61>] entry_SYSCALL64_slow_path+0x25/0x25
> > 
> > After encountering this, the system-udevd process seems to be blocked
> > until it is killed when hitting its timeout of 3min.
> > 
> > In analogy to the other accesses to members of quirk in usb_audio_probe(),
> > check for quirk != NULL before accessing its ->media_device.
> > 
> > Fixes: aebb2b89bff0 ("[media] sound/usb: Use Media Controller API to share
> >                       media resources")
> > Signed-off-by: Nicolai Stange <nicstange@...il.com>  
> 
> Reviewed-by: Takashi Iwai <tiwai@...e.de>
> 
> Mauro, please merge through your tree.  I haven't merged MC changes
> into my tree yet.

OK, I'll send this fix together with some other patches in a couple
of days (it needs to go first to linux-next ;) ).

> 
> 
> thanks
> 
> Takashi
> 
> 
> > ---
> >  Applicable to linux-next-20160315.
> > 
> >  sound/usb/card.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/sound/usb/card.c b/sound/usb/card.c
> > index 63244bb..479621e 100644
> > --- a/sound/usb/card.c
> > +++ b/sound/usb/card.c
> > @@ -612,7 +612,7 @@ static int usb_audio_probe(struct usb_interface *intf,
> >  	if (err < 0)
> >  		goto __error;
> >  
> > -	if (quirk->media_device) {
> > +	if (quirk && quirk->media_device) {
> >  		/* don't want to fail when media_snd_device_create() fails */
> >  		media_snd_device_create(chip, intf);
> >  	}
> > -- 
> > 2.7.2
> > 
> >   


-- 
Thanks,
Mauro