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authorTakashi Iwai <tiwai@suse.de>2016-11-14 21:46:47 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-11-26 09:56:54 +0100
commit85fcb62a58b281e3bed60ecdc34d1559ba06c9c1 (patch)
treed73aa955fa48fb4938ba33b99c3e64da96f755a1
parente902f10da218c4af481337ed2a090c9bdf739630 (diff)
ALSA: usb-audio: Fix use-after-free of usb_device at disconnect
commit 6ff1a25318ebf688ef9593fe09cd449f6fb4ad31 upstream. The usb-audio driver implements the deferred device disconnection for the device in use. In this mode, the disconnection callback returns immediately while the actual ALSA card object removal happens later when all files get closed. As Shuah reported, this code flow, however, leads to a use-after-free, detected by KASAN: BUG: KASAN: use-after-free in snd_usb_audio_free+0x134/0x160 [snd_usb_audio] at addr ffff8801c863ce10 Write of size 8 by task pulseaudio/2244 Call Trace: [<ffffffff81b31473>] dump_stack+0x67/0x94 [<ffffffff81564ef1>] kasan_object_err+0x21/0x70 [<ffffffff8156518a>] kasan_report_error+0x1fa/0x4e0 [<ffffffff81564ad7>] ? kasan_slab_free+0x87/0xb0 [<ffffffff81565733>] __asan_report_store8_noabort+0x43/0x50 [<ffffffffa0fc0f54>] ? snd_usb_audio_free+0x134/0x160 [snd_usb_audio] [<ffffffffa0fc0f54>] snd_usb_audio_free+0x134/0x160 [snd_usb_audio] [<ffffffffa0fc0fb1>] snd_usb_audio_dev_free+0x31/0x40 [snd_usb_audio] [<ffffffff8243c78a>] __snd_device_free+0x12a/0x210 [<ffffffff8243d1f5>] snd_device_free_all+0x85/0xd0 [<ffffffff8242cae4>] release_card_device+0x34/0x130 [<ffffffff81ef1846>] device_release+0x76/0x1e0 [<ffffffff81b37ad7>] kobject_release+0x107/0x370 ..... Object at ffff8801c863cc80, in cache kmalloc-2048 size: 2048 Allocated: [<ffffffff810804eb>] save_stack_trace+0x2b/0x50 [<ffffffff81564296>] save_stack+0x46/0xd0 [<ffffffff8156450d>] kasan_kmalloc+0xad/0xe0 [<ffffffff81560d1a>] kmem_cache_alloc_trace+0xfa/0x240 [<ffffffff8214ea47>] usb_alloc_dev+0x57/0xc90 [<ffffffff8216349d>] hub_event+0xf1d/0x35f0 .... Freed: [<ffffffff810804eb>] save_stack_trace+0x2b/0x50 [<ffffffff81564296>] save_stack+0x46/0xd0 [<ffffffff81564ac1>] kasan_slab_free+0x71/0xb0 [<ffffffff81560929>] kfree+0xd9/0x280 [<ffffffff8214de6e>] usb_release_dev+0xde/0x110 [<ffffffff81ef1846>] device_release+0x76/0x1e0 .... It's the code trying to clear drvdata of the assigned usb_device where the usb_device itself was already released in usb_release_dev() after the disconnect callback. This patch fixes it by checking whether the code path is via the disconnect callback, i.e. chip->shutdown flag is set. Fixes: 79289e24194a ('ALSA: usb-audio: Refer to chip->usb_id for quirks...') Reported-and-tested-by: Shuah Khan <shuahkh@osg.samsung.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--sound/usb/card.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/sound/usb/card.c b/sound/usb/card.c
index 9e5276d6dda0..2ddc034673a8 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -315,7 +315,8 @@ static int snd_usb_audio_free(struct snd_usb_audio *chip)
snd_usb_endpoint_free(ep);
mutex_destroy(&chip->mutex);
- dev_set_drvdata(&chip->dev->dev, NULL);
+ if (!atomic_read(&chip->shutdown))
+ dev_set_drvdata(&chip->dev->dev, NULL);
kfree(chip);
return 0;
}