On Tue, 23 Jul 2019 19:03:29 +0200,
Andrey Konovalov wrote:
>
> (Takashi, with your helper check syzkaller now generates a new bug
> report (not reported by syzbot yet due to breakage during kernel boot
> on 5.3-rc1, so see below) and I guess this has to do with a missing ep
> != NULL check).
>
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> CPU: 1 PID: 74 Comm: kworker/1:1 Not tainted 5.3.0-rc1+ #40
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> Workqueue: usb_hub_wq hub_event
> RIP: 0010:snd_usb_pipe_sanity_check+0x80/0x130 sound/usb/helper.c:75
> Code: 48 c1 ea 03 80 3c 02 00 0f 85 b3 00 00 00 48 8b 6d 00 c1 eb 1e
> 48 b8 00 00 00 00 00 fc ff df 48 8d 7d 03 48 89 fa 48 c1 ea 03 <0f> b6
> 04 02 48 89 fa 83 e2 07 38 d0 7f 04 84 c0 75 7b 48 b8 00 00
> RSP: 0018:ffff88806c33f0a8 EFLAGS: 00010246
> RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff833819c2
> RDX: 0000000000000000 RSI: ffffffff833819dc RDI: 0000000000000003
> RBP: 0000000000000000 R08: ffff88806c330000 R09: fffffbfff0d1a792
> R10: fffffbfff0d1a791 R11: ffffffff868d3c8f R12: 0000000000000000
> R13: dffffc0000000000 R14: ffff88806975cc80 R15: ffff88806975c4a0
> FS: 0000000000000000(0000) GS:ffff88806d100000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fcc3a48c000 CR3: 000000006861c003 CR4: 0000000000160ee0
> Call Trace:
> snd_usb_accessmusic_boot_quirk sound/usb/quirks.c:835 [inline]
> snd_usb_apply_boot_quirk+0xa19/0xc60 sound/usb/quirks.c:1267
> usb_audio_probe+0x2ec/0x1f40 sound/usb/card.c:576
(snip)
So it's a NULL pointer returned from usb_pipe_endpoint() with an
invalid pipe. The fix patch is attached below.
thanks,
Takashi
-- 8< --
From: Takashi Iwai <tiwai@xxxxxxx>
Subject: [PATCH] ALSA: usb-audio: Fix NULL dereference at pipe sanity check
The newly introduced helper for a sanity check of a pipe causes an
Oops due to the NULL pointer returned from usb_pipe_endpoint() with an
invalid pipe. Let's fix it.
Fixes: 801ebf1043ae ("ALSA: usb-audio: Sanity checks for each pipe and EP types")
Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
sound/usb/helper.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/sound/usb/helper.c b/sound/usb/helper.c
index 71d5f540334a..919d69e0aba3 100644
--- a/sound/usb/helper.c
+++ b/sound/usb/helper.c
@@ -72,6 +72,8 @@ int snd_usb_pipe_sanity_check(struct usb_device *dev, unsigned int pipe)
struct usb_host_endpoint *ep;
ep = usb_pipe_endpoint(dev, pipe);
+ if (!ep)
+ return -EINVAL;
if (usb_pipetype(pipe) != pipetypes[usb_endpoint_type(&ep->desc)])
return -EINVAL;
return 0;
--
2.16.4
