On Tue, 10 Oct 2017 13:20:14 +0200,
Andrey Konovalov wrote:
>
> On Tue, Oct 10, 2017 at 12:10 AM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> > On Mon, 09 Oct 2017 19:50:39 +0200,
> > Andrey Konovalov wrote:
> >>
> >> Hi!
> >>
> >> I've got the following report while fuzzing the kernel with syzkaller.
> >>
> >> On commit 8a5776a5f49812d29fe4b2d0a2d71675c3facf3f (4.14-rc4).
> >>
> >> gadgetfs: bound to dummy_udc driver
> >> usb 1-1: new full-speed USB device number 2 using dummy_hcd
> >> gadgetfs: connected
> >> gadgetfs: disconnected
> >> gadgetfs: connected
> >> usb 1-1: config 1 has an invalid interface number: 1 but max is 0
> >> usb 1-1: config 1 has 2 interfaces, different from the descriptor's value: 1
> >> usb 1-1: config 1 interface 0 altsetting 0 endpoint 0x81 has an
> >> invalid bInterval 0, changing to 10
> >> usb 1-1: too many endpoints for config 1 interface 1 altsetting 174:
> >> 131, using maximum allowed: 30
> >> usb 1-1: config 1 interface 1 altsetting 174 has 0 endpoint
> >> descriptors, different from the interface de
> >> scriptor's value: 131
> >> usb 1-1: config 1 interface 1 has no altsetting 0
> >> usb 1-1: New USB device found, idVendor=0dba, idProduct=1000
> >> usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=252
> >> usb 1-1: SerialNumber: a
> >> gadgetfs: configuration #1
> >> hub 1-1:1.0: USB hub found
> >> hub 1-1:1.0: config failed, can't read hub descriptor (err -22)
> >> snd-usb-audio: probe of 1-1:1.0 failed with error -22
> >> ==================================================================
> >> BUG: KASAN: use-after-free in snd_usb_mixer_interrupt+0x604/0x6f0
> >> Read of size 8 at addr ffff8800636f8900 by task swapper/1/0
> >
> > A bad news for a sleepless night...
> >
> > It's a stray URB that isn't properly killed when the usb-audio mixer
> > interface gets the error at probe. The patch below should fix it.
> > I'm going to wrap up with a proper description later.
>
> This fixes the crash.
>
> Thanks!
>
> Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Thanks, I'll queue the fix to for-linus branch.
FWIW, below is the patch with the description.
Takashi
-- 8< --
From: Takashi Iwai <tiwai@xxxxxxx>
Subject: [PATCH] ALSA: usb-audio: Kill stray URB at exiting
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 | 2 ++
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 9732edf77f86..91bc8f18791e 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -2234,6 +2234,9 @@ 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);
+
kfree(mixer->id_elems);
if (mixer->urb) {
kfree(mixer->urb->transfer_buffer);
@@ -2584,8 +2587,13 @@ int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif,
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
diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
index 2b4b067646ab..545d99b09706 100644
--- 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 */
--
2.14.2
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