[PATCH] net: usb: asix: fill null-ptr-deref in asix_suspend

[PATCH] net: usb: asix: fill null-ptr-deref in asix_suspend

[Andrey Konovalov]

When asix_suspend() is called dev->driver_priv might not have been
assigned a value, so we need to check that it's not NULL.

Found by syzkaller.

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.14.0-rc4-43422-geccacdd69a8c #400
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: usb_hub_wq hub_event
task: ffff88006bb36300 task.stack: ffff88006bba8000
RIP: 0010:asix_suspend+0x76/0xc0 drivers/net/usb/asix_devices.c:629
RSP: 0018:ffff88006bbae718 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff880061ba3b80 RCX: 1ffff1000c34d644
RDX: 0000000000000001 RSI: 0000000000000402 RDI: 0000000000000008
RBP: ffff88006bbae738 R08: 1ffff1000d775cad R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800630a8b40
R13: 0000000000000000 R14: 0000000000000402 R15: ffff880061ba3b80
FS:  0000000000000000(0000) GS:ffff88006c600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff33cf89000 CR3: 0000000061c0a000 CR4: 00000000000006f0
Call Trace:
 usb_suspend_interface drivers/usb/core/driver.c:1209
 usb_suspend_both+0x27f/0x7e0 drivers/usb/core/driver.c:1314
 usb_runtime_suspend+0x41/0x120 drivers/usb/core/driver.c:1852
 __rpm_callback+0x339/0xb60 drivers/base/power/runtime.c:334
 rpm_callback+0x106/0x220 drivers/base/power/runtime.c:461
 rpm_suspend+0x465/0x1980 drivers/base/power/runtime.c:596
 __pm_runtime_suspend+0x11e/0x230 drivers/base/power/runtime.c:1009
 pm_runtime_put_sync_autosuspend ./include/linux/pm_runtime.h:251
 usb_new_device+0xa37/0x1020 drivers/usb/core/hub.c:2487
 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
Code: 8d 7c 24 20 48 89 fa 48 c1 ea 03 80 3c 02 00 75 5b 48 b8 00 00
00 00 00 fc ff df 4d 8b 6c 24 20 49 8d 7d 08 48 89 fa 48 c1 ea 03 <80>
3c 02 00 75 34 4d 8b 6d 08 4d 85 ed 74 0b e8 26 2b 51 fd 4c
RIP: asix_suspend+0x76/0xc0 RSP: ffff88006bbae718
---[ end trace dfc4f5649284342c ]---

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 drivers/net/usb/asix_devices.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c
index b2ff88e69a81..743416be84f3 100644
--- a/drivers/net/usb/asix_devices.c
+++ b/drivers/net/usb/asix_devices.c
@@ -626,7 +626,7 @@ static int asix_suspend(struct usb_interface *intf, pm_message_t message)
 	struct usbnet *dev = usb_get_intfdata(intf);
 	struct asix_common_private *priv = dev->driver_priv;
 
-	if (priv->suspend)
+	if (priv && priv->suspend)
 		priv->suspend(dev);
 
 	return usbnet_suspend(intf, message);
-- 
2.15.0.403.gc27cc4dac6-goog

Re: [PATCH] net: usb: asix: fill null-ptr-deref in asix_suspend

[David Miller]

From: Andrey Konovalov <andreyknvl@google.com>
Date: Thu,  2 Nov 2017 21:26:59 +0100

> When asix_suspend() is called dev->driver_priv might not have been
> assigned a value, so we need to check that it's not NULL.
> 
> Found by syzkaller.
 ...
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Applied, thank you.

Re: [PATCH] net: usb: asix: fill null-ptr-deref in asix_suspend

[Oliver Neukum]

Am Donnerstag, den 02.11.2017, 21:26 +0100 schrieb Andrey Konovalov:
> When asix_suspend() is called dev->driver_priv might not have been
> assigned a value, so we need to check that it's not NULL.
> 
> Found by syzkaller.

Hi,

1. if that happens on suspend, it will also happen on resume
2. Will a device work after that? The appropriate fix may be to wait
until the device is properly initialized.

	Regards
		Oliver

Re: [PATCH] net: usb: asix: fill null-ptr-deref in asix_suspend

[Andrey Konovalov]

On Mon, Nov 6, 2017 at 10:49 AM, Oliver Neukum <oneukum@suse.com> wrote:
> Am Donnerstag, den 02.11.2017, 21:26 +0100 schrieb Andrey Konovalov:
>> When asix_suspend() is called dev->driver_priv might not have been
>> assigned a value, so we need to check that it's not NULL.
>>
>> Found by syzkaller.
>
> Hi,

Hi Oliver,

>
> 1. if that happens on suspend, it will also happen on resume

Indeed, got crashes in asix_resume() tonight as well. Mailed v2.

> 2. Will a device work after that? The appropriate fix may be to wait
> until the device is properly initialized.

This shouldn't affect real devices as far as I understand. The crash
can be caused by a crafted malicious device.

Go ahead if you see a better way to fix this, my patch is more of a
hot fix trying to prevent the crashes.

Thanks!

>
>         Regards
>                 Oliver
>

Re: [PATCH] net: usb: asix: fill null-ptr-deref in asix_suspend

[Oliver Neukum]

Am Montag, den 06.11.2017, 13:30 +0100 schrieb Andrey Konovalov:
> On Mon, Nov 6, 2017 at 10:49 AM, Oliver Neukum <oneukum@suse.com> wrote:
> > 
> > 
> > 2. Will a device work after that? The appropriate fix may be to wait
> > until the device is properly initialized.
> 
> This shouldn't affect real devices as far as I understand. The crash
> can be caused by a crafted malicious device.

Hi!

Hm. That seems strange as driver_priv is kmalloced. Do you
still have a descriptor that causes this?
Shouldn't we rather reject such a broken device?

	Regards
		Oliver

Re: [PATCH] net: usb: asix: fill null-ptr-deref in asix_suspend

[Andrey Konovalov]

On Mon, Nov 6, 2017 at 4:20 PM, Oliver Neukum <oneukum@suse.com> wrote:
> Am Montag, den 06.11.2017, 13:30 +0100 schrieb Andrey Konovalov:
>> On Mon, Nov 6, 2017 at 10:49 AM, Oliver Neukum <oneukum@suse.com> wrote:
>> >
>> >
>> > 2. Will a device work after that? The appropriate fix may be to wait
>> > until the device is properly initialized.
>>
>> This shouldn't affect real devices as far as I understand. The crash
>> can be caused by a crafted malicious device.
>
> Hi!
>
> Hm. That seems strange as driver_priv is kmalloced. Do you
> still have a descriptor that causes this?
> Shouldn't we rather reject such a broken device?

I do have a way to reproduce this.

As far as I understand, for this particular device ax88172_bind() is
called, which doesn't assign anything to dev->driver_priv, so that's
why it is NULL in suspend() and resume().

>
>         Regards
>                 Oliver
>

Re: [PATCH] net: usb: asix: fill null-ptr-deref in asix_suspend

[Oliver Neukum]

Am Montag, den 06.11.2017, 17:05 +0100 schrieb Andrey Konovalov:
> On Mon, Nov 6, 2017 at 4:20 PM, Oliver Neukum <oneukum@suse.com> wrote:
> > 

> I do have a way to reproduce this.
> 
> As far as I understand, for this particular device ax88172_bind() is
> called, which doesn't assign anything to dev->driver_priv, so that's
> why it is NULL in suspend() and resume().

Thanks and ouch. That means it never worked for those devices.
That makes this a rather serious bug and your fix is right.

	Regards
		Oliver