Re: [PATCH 3.18 08/19] ALSA: usb-audio: Kill stray URB at exiting
From: Takashi Iwai
Date: Mon Oct 16 2017 - 14:50:10 EST
On Mon, 16 Oct 2017 18:11:59 +0200,
Greg Kroah-Hartman wrote:
>
> 3.18-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> 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
> @@ -2157,6 +2157,9 @@ 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);
> @@ -2501,8 +2504,13 @@ void snd_usb_mixer_disconnect(struct lis
> /* stop any bus activity of a mixer */
> static void snd_usb_mixer_inactivate(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;
This looks applied wrongly, as already caught by kbuild bot.
The snd_usb_mixer_disconnect() argument changed in the later kernel,
thus the patch couldn't be applied cleanly as is.
Below is the revised patch (but only compile-tested).
thanks,
Takashi
-- 8< --
From: Takashi Iwai <tiwai@xxxxxxx>
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@xxxxxxxxxx>
Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
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 */
--
2.14.2