On Tue, 17 Oct 2017 14:46:53 +0200, Arnd Bergmann wrote:

On Tue, Oct 17, 2017 at 12:22 PM, Olof's autobuilder build@lixom.net wrote:

...

Warnings:

  9 sound/usb/mixer.c:2161:27: warning: passing argument 1 of 'snd_usb_mixer_disconnect' from incompatible pointer type [-Wincompatible-pointer-types]

This broke after backporting 124751d5e63c ("ALSA: usb-audio: Kill stray URB at exiting") into linux-3.18.

The interface was changed in commit a6cece9d8199 ("ALSA: usb-audio: Pass direct struct pointer instead of list_head"), which was merged in linux-3.19.

I don't immediately see how this can be fixed. Backporting a6cece9d8199 would probably work.

I already posted the revised patch yesterday, but apparently this seems overlooked:

Subject: Re: [PATCH 3.18 08/19] ALSA: usb-audio: Kill stray URB at exiting From: Takashi Iwai tiwai@suse.de Date: Mon, 16 Oct 2017 20:50:02 +0200 Message-ID: s5hpo9nylk5.wl-tiwai@suse.de

The same patch is attached below.

Greg, could you replace the broken one?

thanks,

Takashi

-- 8< -- From: Takashi Iwai tiwai@suse.de Subject: [PATCH 3.18.y] ALSA: usb-audio: Kill stray URB at exiting

commit 124751d5e63c823092060074bd0abaae61aaa9c4 upstream.

USB-audio driver may leave a stray URB for the mixer interrupt when it exits by some error during probe. This leads to a use-after-free error as spotted by syzkaller like: ================================================================== BUG: KASAN: use-after-free in snd_usb_mixer_interrupt+0x604/0x6f0 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:16 dump_stack+0x292/0x395 lib/dump_stack.c:52 print_address_description+0x78/0x280 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 kasan_report+0x23d/0x350 mm/kasan/report.c:409 __asan_report_load8_noabort+0x19/0x20 mm/kasan/report.c:430 snd_usb_mixer_interrupt+0x604/0x6f0 sound/usb/mixer.c:2490 __usb_hcd_giveback_urb+0x2e0/0x650 drivers/usb/core/hcd.c:1779 ....

Allocated by task 1484: save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551 kmem_cache_alloc_trace+0x11e/0x2d0 mm/slub.c:2772 kmalloc ./include/linux/slab.h:493 kzalloc ./include/linux/slab.h:666 snd_usb_create_mixer+0x145/0x1010 sound/usb/mixer.c:2540 create_standard_mixer_quirk+0x58/0x80 sound/usb/quirks.c:516 snd_usb_create_quirk+0x92/0x100 sound/usb/quirks.c:560 create_composite_quirk+0x1c4/0x3e0 sound/usb/quirks.c:59 snd_usb_create_quirk+0x92/0x100 sound/usb/quirks.c:560 usb_audio_probe+0x1040/0x2c10 sound/usb/card.c:618 ....

Freed by task 1484: save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:524 slab_free_hook mm/slub.c:1390 slab_free_freelist_hook mm/slub.c:1412 slab_free mm/slub.c:2988 kfree+0xf6/0x2f0 mm/slub.c:3919 snd_usb_mixer_free+0x11a/0x160 sound/usb/mixer.c:2244 snd_usb_mixer_dev_free+0x36/0x50 sound/usb/mixer.c:2250 __snd_device_free+0x1ff/0x380 sound/core/device.c:91 snd_device_free_all+0x8f/0xe0 sound/core/device.c:244 snd_card_do_free sound/core/init.c:461 release_card_device+0x47/0x170 sound/core/init.c:181 device_release+0x13f/0x210 drivers/base/core.c:814 ....

Actually such a URB is killed properly at disconnection when the device gets probed successfully, and what we need is to apply it for the error-path, too.

In this patch, we apply snd_usb_mixer_disconnect() at releasing. Also introduce a new flag, disconnected, to struct usb_mixer_interface for not performing the disconnection procedure twice.

Reported-by: Andrey Konovalov andreyknvl@google.com Tested-by: Andrey Konovalov andreyknvl@google.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/usb/mixer.c | 12 ++++++++++-- sound/usb/mixer.h | 1 + 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 1ceeb9e875a4..d0bbc7b32190 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2157,6 +2157,9 @@ static int parse_audio_unit(struct mixer_build *state, int unitid)

static void snd_usb_mixer_free(struct usb_mixer_interface *mixer) { + /* kill pending URBs */ + snd_usb_mixer_disconnect(&mixer->list); + kfree(mixer->id_elems); if (mixer->urb) { kfree(mixer->urb->transfer_buffer); @@ -2493,8 +2496,13 @@ void snd_usb_mixer_disconnect(struct list_head *p) struct usb_mixer_interface *mixer;

mixer = list_entry(p, struct usb_mixer_interface, list); - usb_kill_urb(mixer->urb); - usb_kill_urb(mixer->rc_urb); + if (mixer->disconnected) + return; + if (mixer->urb) + usb_kill_urb(mixer->urb); + if (mixer->rc_urb) + usb_kill_urb(mixer->rc_urb); + mixer->disconnected = true; }

#ifdef CONFIG_PM diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h index 73b1f649447b..cdff31de12d4 100644 --- a/sound/usb/mixer.h +++ b/sound/usb/mixer.h @@ -23,6 +23,7 @@ struct usb_mixer_interface {

u8 audigy2nx_leds[3]; u8 xonar_u1_status; + bool disconnected; };

#define MAX_CHANNELS 16 /* max logical channels */