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Groups > linux.kernel > #1737477 > unrolled thread

usb/sounds: slab-out-of-bounds read in snd_usb_create_streams

Started byAndrey Konovalov <andreyknvl@google.com>
First post2017-09-22 15:00 +0200
Last post2017-09-22 16:30 +0200
Articles 4 — 2 participants

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Contents

  usb/sounds: slab-out-of-bounds read in snd_usb_create_streams Andrey Konovalov <andreyknvl@google.com> - 2017-09-22 15:00 +0200
    Re: usb/sounds: slab-out-of-bounds read in snd_usb_create_streams Takashi Iwai <tiwai@suse.de> - 2017-09-22 15:20 +0200
      Re: usb/sounds: slab-out-of-bounds read in snd_usb_create_streams Andrey Konovalov <andreyknvl@google.com> - 2017-09-22 16:00 +0200
        Re: usb/sounds: slab-out-of-bounds read in snd_usb_create_streams Takashi Iwai <tiwai@suse.de> - 2017-09-22 16:30 +0200

#1737477 — usb/sounds: slab-out-of-bounds read in snd_usb_create_streams

FromAndrey Konovalov <andreyknvl@google.com>
Date2017-09-22 15:00 +0200
Subjectusb/sounds: slab-out-of-bounds read in snd_usb_create_streams
Message-ID<usvIJ-6c6-1@gated-at.bofh.it>
Hi!

I've got the following report while fuzzing the kernel with syzkaller.

On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).

It seems that there's no check that control_header has enough space
for uac1_ac_header_descriptor in snd_usb_create_streams().

==================================================================
BUG: KASAN: slab-out-of-bounds in usb_audio_probe+0x27b2/0x2ab0
Read of size 1 at addr ffff88006b83a9e8 by task kworker/0:1/24

CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.14.0-rc1-42251-gebb2c2437d80 #224
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
 __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+0x22f/0x340 mm/kasan/report.c:409
 __asan_report_load1_noabort+0x19/0x20 mm/kasan/report.c:427
 snd_usb_create_streams sound/usb/card.c:248
 usb_audio_probe+0x27b2/0x2ab0 sound/usb/card.c:605
 usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
 really_probe drivers/base/dd.c:413
 driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
 __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
 bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
 __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
 device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
 bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
 device_add+0xd0b/0x1660 drivers/base/core.c:1835
 usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
 generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
 usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
 really_probe drivers/base/dd.c:413
 driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
 __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
 bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
 __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
 device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
 bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
 device_add+0xd0b/0x1660 drivers/base/core.c:1835
 usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
 hub_port_connect drivers/usb/core/hub.c:4903
 hub_port_connect_change drivers/usb/core/hub.c:5009
 port_event drivers/usb/core/hub.c:5115
 hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
 process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
 worker_thread+0x221/0x1850 kernel/workqueue.c:2253
 kthread+0x3a1/0x470 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Allocated by task 24:
 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
 __kmalloc+0x14e/0x310 mm/slub.c:3782
 kmalloc ./include/linux/slab.h:498
 usb_get_configuration+0x372/0x2a60 drivers/usb/core/config.c:848
 usb_enumerate_device drivers/usb/core/hub.c:2290
 usb_new_device+0xaae/0x1020 drivers/usb/core/hub.c:2426
 hub_port_connect drivers/usb/core/hub.c:4903
 hub_port_connect_change drivers/usb/core/hub.c:5009
 port_event drivers/usb/core/hub.c:5115
 hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
 process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
 worker_thread+0x221/0x1850 kernel/workqueue.c:2253
 kthread+0x3a1/0x470 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Freed by task 4048:
 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
 free_rb_tree_fname+0x8a/0xe0 fs/ext4/dir.c:402
 ext4_htree_free_dir_info fs/ext4/dir.c:424
 ext4_release_dir+0x49/0x70 fs/ext4/dir.c:622
 __fput+0x33e/0x800 fs/file_table.c:210
 ____fput+0x1a/0x20 fs/file_table.c:244
 task_work_run+0x1af/0x280 kernel/task_work.c:112
 tracehook_notify_resume ./include/linux/tracehook.h:191
 exit_to_usermode_loop+0x1e1/0x220 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197
 syscall_return_slowpath+0x414/0x480 arch/x86/entry/common.c:266
 entry_SYSCALL_64_fastpath+0xc0/0xc2 arch/x86/entry/entry_64.S:238

The buggy address belongs to the object at ffff88006b83a9c0
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 40 bytes inside of
 64-byte region [ffff88006b83a9c0, ffff88006b83aa00)
The buggy address belongs to the page:
page:ffffea0001ae0e80 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0x100000000000100(slab)
raw: 0100000000000100 0000000000000000 0000000000000000 00000001802a002a
raw: 0000000000000000 0000000100000001 ffff88006c403800 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88006b83a880: fc fc fc fc 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff88006b83a900: fb fb fb fb fb fb fb fb fc fc fc fc 00 00 00 00
>ffff88006b83a980: 00 00 fc fc fc fc fc fc 00 00 00 00 07 fc fc fc
                                                          ^
 ffff88006b83aa00: fc fc fc fc 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff88006b83aa80: 00 00 00 00 00 00 00 00 fc fc fc fc 00 00 00 00
==================================================================

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#1737491

FromTakashi Iwai <tiwai@suse.de>
Date2017-09-22 15:20 +0200
Message-ID<usw25-6xr-5@gated-at.bofh.it>
In reply to#1737477
On Fri, 22 Sep 2017 14:56:06 +0200,
Andrey Konovalov wrote:
> 
> Hi!
> 
> I've got the following report while fuzzing the kernel with syzkaller.
> 
> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
> 
> It seems that there's no check that control_header has enough space
> for uac1_ac_header_descriptor in snd_usb_create_streams().

Indeed, this might be an issue.
Does the patch below fix the problem?


Takashi

---
diff --git a/sound/usb/card.c b/sound/usb/card.c
index 3dc36d913550..fc969efbb37c 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -221,6 +221,7 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 	struct usb_interface_descriptor *altsd;
 	void *control_header;
 	int i, protocol;
+	int rest_bytes;
 
 	/* find audiocontrol interface */
 	host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
@@ -235,6 +236,13 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 		return -EINVAL;
 	}
 
+	rest_bytes = (void *)(host_iface->extra + host_iface->extralen) -
+		control_header;
+	if (rest_bytes <= 0) {
+		dev_err(&dev->dev, "invalid control header\n");
+		return -EINVAL;
+	}
+
 	switch (protocol) {
 	default:
 		dev_warn(&dev->dev,
@@ -245,11 +253,21 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 	case UAC_VERSION_1: {
 		struct uac1_ac_header_descriptor *h1 = control_header;
 
+		if (rest_bytes < sizeof(*h1)) {
+			dev_err(&dev->dev, "too short v1 buffer descriptor\n");
+			return -EINVAL;
+		}
+
 		if (!h1->bInCollection) {
 			dev_info(&dev->dev, "skipping empty audio interface (v1)\n");
 			return -EINVAL;
 		}
 
+		if (rest_bytes < h1->bLength) {
+			dev_err(&dev->dev, "invalid buffer length (v1)\n");
+			return -EINVAL;
+		}
+
 		if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
 			dev_err(&dev->dev, "invalid UAC_HEADER (v1)\n");
 			return -EINVAL;

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#1737515

FromAndrey Konovalov <andreyknvl@google.com>
Date2017-09-22 16:00 +0200
Message-ID<uswEN-6Ku-5@gated-at.bofh.it>
In reply to#1737491
On Fri, Sep 22, 2017 at 3:19 PM, Takashi Iwai <tiwai@suse.de> wrote:
> On Fri, 22 Sep 2017 14:56:06 +0200,
> Andrey Konovalov wrote:
>>
>> Hi!
>>
>> I've got the following report while fuzzing the kernel with syzkaller.
>>
>> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
>>
>> It seems that there's no check that control_header has enough space
>> for uac1_ac_header_descriptor in snd_usb_create_streams().
>
> Indeed, this might be an issue.
> Does the patch below fix the problem?

I believe it does. It does fix the crash with my reproducer.

I'm not sure if the (rest_bytes <= 0) check is actually needed though.
It seems that if snd_usb_find_csint_desc() returns a non-null value,
it'll always be within the buffer.

Tested-by: Andrey Konovalov <andreyknvl@google.com>

>
>
> Takashi
>
> ---
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 3dc36d913550..fc969efbb37c 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -221,6 +221,7 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
>         struct usb_interface_descriptor *altsd;
>         void *control_header;
>         int i, protocol;
> +       int rest_bytes;
>
>         /* find audiocontrol interface */
>         host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
> @@ -235,6 +236,13 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
>                 return -EINVAL;
>         }
>
> +       rest_bytes = (void *)(host_iface->extra + host_iface->extralen) -
> +               control_header;
> +       if (rest_bytes <= 0) {
> +               dev_err(&dev->dev, "invalid control header\n");
> +               return -EINVAL;
> +       }
> +
>         switch (protocol) {
>         default:
>                 dev_warn(&dev->dev,
> @@ -245,11 +253,21 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
>         case UAC_VERSION_1: {
>                 struct uac1_ac_header_descriptor *h1 = control_header;
>
> +               if (rest_bytes < sizeof(*h1)) {
> +                       dev_err(&dev->dev, "too short v1 buffer descriptor\n");
> +                       return -EINVAL;
> +               }
> +
>                 if (!h1->bInCollection) {
>                         dev_info(&dev->dev, "skipping empty audio interface (v1)\n");
>                         return -EINVAL;
>                 }
>
> +               if (rest_bytes < h1->bLength) {
> +                       dev_err(&dev->dev, "invalid buffer length (v1)\n");
> +                       return -EINVAL;
> +               }
> +
>                 if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
>                         dev_err(&dev->dev, "invalid UAC_HEADER (v1)\n");
>                         return -EINVAL;
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.

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#1737530

FromTakashi Iwai <tiwai@suse.de>
Date2017-09-22 16:30 +0200
Message-ID<usx7P-78K-3@gated-at.bofh.it>
In reply to#1737515
On Fri, 22 Sep 2017 15:55:17 +0200,
Andrey Konovalov wrote:
> 
> On Fri, Sep 22, 2017 at 3:19 PM, Takashi Iwai <tiwai@suse.de> wrote:
> > On Fri, 22 Sep 2017 14:56:06 +0200,
> > Andrey Konovalov wrote:
> >>
> >> Hi!
> >>
> >> I've got the following report while fuzzing the kernel with syzkaller.
> >>
> >> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
> >>
> >> It seems that there's no check that control_header has enough space
> >> for uac1_ac_header_descriptor in snd_usb_create_streams().
> >
> > Indeed, this might be an issue.
> > Does the patch below fix the problem?
> 
> I believe it does. It does fix the crash with my reproducer.
> 
> I'm not sure if the (rest_bytes <= 0) check is actually needed though.

It's superfluous, but safer is safer, and this check is cheap.

> It seems that if snd_usb_find_csint_desc() returns a non-null value,
> it'll always be within the buffer.
> 
> Tested-by: Andrey Konovalov <andreyknvl@google.com>

Thanks, I'm going to queue it.
FWIW, below is the official patch.


Takashi

-- 8< --
From: Takashi Iwai <tiwai@suse.de>
Subject: [PATCH] ALSA: usb-audio: Check out-of-bounds access by corrupted
 buffer descriptor

When a USB-audio device receives a maliciously adjusted or corrupted
buffer descriptor, the USB-audio driver may access an out-of-bounce
value at its parser.  This was detected by syzkaller, something like:

  BUG: KASAN: slab-out-of-bounds in usb_audio_probe+0x27b2/0x2ab0
  Read of size 1 at addr ffff88006b83a9e8 by task kworker/0:1/24
  CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.14.0-rc1-42251-gebb2c2437d80 #224
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Workqueue: usb_hub_wq hub_event
  Call Trace:
   __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+0x22f/0x340 mm/kasan/report.c:409
   __asan_report_load1_noabort+0x19/0x20 mm/kasan/report.c:427
   snd_usb_create_streams sound/usb/card.c:248
   usb_audio_probe+0x27b2/0x2ab0 sound/usb/card.c:605
   usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
   really_probe drivers/base/dd.c:413
   driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
   __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
   bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
   __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
   device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
   bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
   device_add+0xd0b/0x1660 drivers/base/core.c:1835
   usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
   generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
   usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
   really_probe drivers/base/dd.c:413
   driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
   __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
   bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
   __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
   device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
   bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
   device_add+0xd0b/0x1660 drivers/base/core.c:1835
   usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
   hub_port_connect drivers/usb/core/hub.c:4903
   hub_port_connect_change drivers/usb/core/hub.c:5009
   port_event drivers/usb/core/hub.c:5115
   hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
   process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
   worker_thread+0x221/0x1850 kernel/workqueue.c:2253
   kthread+0x3a1/0x470 kernel/kthread.c:231
   ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

This patch adds the checks of out-of-bounce accesses at appropriate
places and bails out when it goes out of the given buffer.

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/card.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 3dc36d913550..23d1d23aefec 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -221,6 +221,7 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 	struct usb_interface_descriptor *altsd;
 	void *control_header;
 	int i, protocol;
+	int rest_bytes;
 
 	/* find audiocontrol interface */
 	host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
@@ -235,6 +236,15 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 		return -EINVAL;
 	}
 
+	rest_bytes = (void *)(host_iface->extra + host_iface->extralen) -
+		control_header;
+
+	/* just to be sure -- this shouldn't hit at all */
+	if (rest_bytes <= 0) {
+		dev_err(&dev->dev, "invalid control header\n");
+		return -EINVAL;
+	}
+
 	switch (protocol) {
 	default:
 		dev_warn(&dev->dev,
@@ -245,11 +255,21 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 	case UAC_VERSION_1: {
 		struct uac1_ac_header_descriptor *h1 = control_header;
 
+		if (rest_bytes < sizeof(*h1)) {
+			dev_err(&dev->dev, "too short v1 buffer descriptor\n");
+			return -EINVAL;
+		}
+
 		if (!h1->bInCollection) {
 			dev_info(&dev->dev, "skipping empty audio interface (v1)\n");
 			return -EINVAL;
 		}
 
+		if (rest_bytes < h1->bLength) {
+			dev_err(&dev->dev, "invalid buffer length (v1)\n");
+			return -EINVAL;
+		}
+
 		if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
 			dev_err(&dev->dev, "invalid UAC_HEADER (v1)\n");
 			return -EINVAL;
-- 
2.14.1

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