This is a note to let you know that I've just added the patch titled ALSA: usb-audio: Kill stray URB at exiting to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: alsa-usb-audio-kill-stray-urb-at-exiting.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 124751d5e63c823092060074bd0abaae61aaa9c4 Mon Sep 17 00:00:00 2001 From: Takashi Iwai <tiwai@xxxxxxx> Date: Tue, 10 Oct 2017 14:10:32 +0200 Subject: ALSA: usb-audio: Kill stray URB at exiting From: Takashi Iwai <tiwai@xxxxxxx> 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@xxxxxxxxxx> Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/usb/mixer.c | 12 ++++++++++-- sound/usb/mixer.h | 2 ++ 2 files changed, 12 insertions(+), 2 deletions(-) --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2161,6 +2161,9 @@ static int parse_audio_unit(struct mixer static void snd_usb_mixer_free(struct usb_mixer_interface *mixer) { + /* kill pending URBs */ + snd_usb_mixer_disconnect(mixer); + kfree(mixer->id_elems); if (mixer->urb) { kfree(mixer->urb->transfer_buffer); @@ -2504,8 +2507,13 @@ _error: void snd_usb_mixer_disconnect(struct usb_mixer_interface *mixer) { - 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 --- a/sound/usb/mixer.h +++ b/sound/usb/mixer.h @@ -22,6 +22,8 @@ struct usb_mixer_interface { struct urb *rc_urb; struct usb_ctrlrequest *rc_setup_packet; u8 rc_buffer[6]; + + bool disconnected; }; #define MAX_CHANNELS 16 /* max logical channels */ Patches currently in stable-queue which might be from tiwai@xxxxxxx are queue-4.4/alsa-caiaq-fix-stray-urb-at-probe-error-path.patch queue-4.4/alsa-seq-fix-copy_from_user-call-inside-lock.patch queue-4.4/alsa-seq-fix-use-after-free-at-creating-a-port.patch queue-4.4/alsa-line6-fix-leftover-urb-at-error-path-during-probe.patch queue-4.4/alsa-usb-audio-kill-stray-urb-at-exiting.patch