On Tue, 10 Oct 2017 13:20:14 +0200, Andrey Konovalov wrote:
On Tue, Oct 10, 2017 at 12:10 AM, Takashi Iwai tiwai@suse.de 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@google.com
Thanks, I'll queue the fix to for-linus branch. FWIW, below is the patch with the description.
Takashi
-- 8< -- From: Takashi Iwai tiwai@suse.de 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@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 | 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 */