[syzbot] KMSAN: uninit-value in asix_mdio_read (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b0a8b5053e8b kmsan: core: add dependency on DEBUG_KERNEL
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=13a4d133b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=46a956fc7a887c60
dashboard link: https://syzkaller.appspot.com/bug?extid=f44badb06036334e867a
compiler: clang version 14.0.0 (/usr/local/google/src/llvm-git-monorepo 2b554920f11c8b763cd9ed9003f4e19b919b8e1f), GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=149fddcbb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17baef25b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f44bad...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline]
BUG: KMSAN: uninit-value in asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline] drivers/net/usb/asix_common.c:497
BUG: KMSAN: uninit-value in asix_mdio_read+0x3c1/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497
asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline]
asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline] drivers/net/usb/asix_common.c:497
asix_mdio_read+0x3c1/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497
asix_mdio_bus_read+0xba/0xe0 drivers/net/usb/asix_common.c:556 drivers/net/usb/asix_common.c:556
__mdiobus_read+0xbf/0x4f0 drivers/net/phy/mdio_bus.c:755 drivers/net/phy/mdio_bus.c:755
mdiobus_read+0xaa/0xf0 drivers/net/phy/mdio_bus.c:862 drivers/net/phy/mdio_bus.c:862
get_phy_c22_id drivers/net/phy/phy_device.c:813 [inline]
get_phy_c22_id drivers/net/phy/phy_device.c:813 [inline] drivers/net/phy/phy_device.c:890
get_phy_device+0x218/0x8b0 drivers/net/phy/phy_device.c:890 drivers/net/phy/phy_device.c:890
mdiobus_scan+0x1c7/0x940
__mdiobus_register+0xe16/0x1200 drivers/net/phy/mdio_bus.c:583 drivers/net/phy/mdio_bus.c:583
__devm_mdiobus_register+0x18f/0x2f0 drivers/net/phy/mdio_devres.c:87 drivers/net/phy/mdio_devres.c:87
ax88772_init_mdio drivers/net/usb/asix_devices.c:676 [inline]
ax88772_init_mdio drivers/net/usb/asix_devices.c:676 [inline] drivers/net/usb/asix_devices.c:786
ax88772_bind+0x10b1/0x1770 drivers/net/usb/asix_devices.c:786 drivers/net/usb/asix_devices.c:786
usbnet_probe+0x1284/0x4140 drivers/net/usb/usbnet.c:1747 drivers/net/usb/usbnet.c:1747
usb_probe_interface+0xf19/0x1600 drivers/usb/core/driver.c:396 drivers/usb/core/driver.c:396
really_probe+0x67d/0x1510 drivers/base/dd.c:596 drivers/base/dd.c:596
__driver_probe_device+0x3e9/0x530 drivers/base/dd.c:751 drivers/base/dd.c:751
driver_probe_device drivers/base/dd.c:781 [inline]
driver_probe_device drivers/base/dd.c:781 [inline] drivers/base/dd.c:898
__device_attach_driver+0x79f/0x1120 drivers/base/dd.c:898 drivers/base/dd.c:898
bus_for_each_drv+0x2d6/0x3f0 drivers/base/bus.c:427 drivers/base/bus.c:427
__device_attach+0x593/0x8e0 drivers/base/dd.c:969 drivers/base/dd.c:969
device_initial_probe+0x4a/0x60 drivers/base/dd.c:1016 drivers/base/dd.c:1016
bus_probe_device+0x17b/0x3e0 drivers/base/bus.c:487 drivers/base/bus.c:487
device_add+0x1d3e/0x2400 drivers/base/core.c:3394 drivers/base/core.c:3394
usb_set_configuration+0x37e9/0x3ed0 drivers/usb/core/message.c:2170 drivers/usb/core/message.c:2170
usb_generic_driver_probe+0x13c/0x300 drivers/usb/core/generic.c:238 drivers/usb/core/generic.c:238
usb_probe_device+0x309/0x570 drivers/usb/core/driver.c:293 drivers/usb/core/driver.c:293
really_probe+0x67d/0x1510 drivers/base/dd.c:596 drivers/base/dd.c:596
__driver_probe_device+0x3e9/0x530 drivers/base/dd.c:751 drivers/base/dd.c:751
driver_probe_device drivers/base/dd.c:781 [inline]
driver_probe_device drivers/base/dd.c:781 [inline] drivers/base/dd.c:898
__device_attach_driver+0x79f/0x1120 drivers/base/dd.c:898 drivers/base/dd.c:898
bus_for_each_drv+0x2d6/0x3f0 drivers/base/bus.c:427 drivers/base/bus.c:427
__device_attach+0x593/0x8e0 drivers/base/dd.c:969 drivers/base/dd.c:969
device_initial_probe+0x4a/0x60 drivers/base/dd.c:1016 drivers/base/dd.c:1016
bus_probe_device+0x17b/0x3e0 drivers/base/bus.c:487 drivers/base/bus.c:487
device_add+0x1d3e/0x2400 drivers/base/core.c:3394 drivers/base/core.c:3394
usb_new_device+0x1b8e/0x2950 drivers/usb/core/hub.c:2563 drivers/usb/core/hub.c:2563
hub_port_connect drivers/usb/core/hub.c:5353 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5497 [inline]
port_event drivers/usb/core/hub.c:5643 [inline]
hub_port_connect drivers/usb/core/hub.c:5353 [inline] drivers/usb/core/hub.c:5725
hub_port_connect_change drivers/usb/core/hub.c:5497 [inline] drivers/usb/core/hub.c:5725
port_event drivers/usb/core/hub.c:5643 [inline] drivers/usb/core/hub.c:5725
hub_event+0x5ad2/0x8910 drivers/usb/core/hub.c:5725 drivers/usb/core/hub.c:5725
process_one_work+0xdb9/0x1820 kernel/workqueue.c:2298 kernel/workqueue.c:2298
process_scheduled_works kernel/workqueue.c:2361 [inline]
process_scheduled_works kernel/workqueue.c:2361 [inline] kernel/workqueue.c:2447
worker_thread+0x1735/0x21f0 kernel/workqueue.c:2447 kernel/workqueue.c:2447
kthread+0x721/0x850 kernel/kthread.c:327 kernel/kthread.c:327
ret_from_fork+0x1f/0x30

Local variable smsr.i created at:
asix_mdio_read+0xbc/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497
asix_mdio_bus_read+0xba/0xe0 drivers/net/usb/asix_common.c:556 drivers/net/usb/asix_common.c:556

CPU: 0 PID: 3145 Comm: kworker/0:3 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usb_hub_wq hub_event

=====================================================


---
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[Pavel Skripkin]

On 12/18/21 14:07, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: b0a8b5053e8b kmsan: core: add dependency on DEBUG_KERNEL
> git tree: https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=13a4d133b00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=46a956fc7a887c60
> dashboard link: https://syzkaller.appspot.com/bug?extid=f44badb06036334e867a
> compiler: clang version 14.0.0 (/usr/local/google/src/llvm-git-monorepo 2b554920f11c8b763cd9ed9003f4e19b919b8e1f), GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=149fddcbb00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17baef25b00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+f44bad...@syzkaller.appspotmail.com
>

The last unhanded case is asix_read_cmd() == 0. Let's handle it...

#syz test: https://github.com/google/kmsan.git master



With regards,
Pavel Skripkin

[Andrew Lunn]

That does not look correct, i think.

asix_read_cmd() == 0 means no error from the read itself. If there is
no error, we should look at the value of smsr and test for bit
AX_HOST_EN. Doing a continue means we just ignore the value returned
by the good read.

I think the correct fix is to look at the value of i. If we have
exceeded 30, we should return -ETIMEDOUT.

Andrew

[Pavel Skripkin]

On 12/19/21 00:42, Andrew Lunn wrote:
> On Sun, Dec 19, 2021 at 12:14:30AM +0300, Pavel Skripkin wrote:
>> On 12/18/21 14:07, syzbot wrote:
>> > Hello,
>> >
>> > syzbot found the following issue on:
>> >
>> > HEAD commit: b0a8b5053e8b kmsan: core: add dependency on DEBUG_KERNEL
>> > git tree: https://github.com/google/kmsan.git master
>> > console output: https://syzkaller.appspot.com/x/log.txt?x=13a4d133b00000
>> > kernel config: https://syzkaller.appspot.com/x/.config?x=46a956fc7a887c60
>> > dashboard link: https://syzkaller.appspot.com/bug?extid=f44badb06036334e867a
>> > compiler: clang version 14.0.0 (/usr/local/google/src/llvm-git-monorepo 2b554920f11c8b763cd9ed9003f4e19b919b8e1f), GNU ld (GNU Binutils for Debian) 2.35.2
>> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=149fddcbb00000
>> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17baef25b00000
>> >
>> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> > Reported-by: syzbot+f44bad...@syzkaller.appspotmail.com
>> >
>>
>> The last unhanded case is asix_read_cmd() == 0. Let's handle it...
>
> That does not look correct, i think.
>
> asix_read_cmd() == 0 means no error from the read itself. If there is
> no error, we should look at the value of smsr and test for bit

As far as I understand asix_read_cmd() == 0 means 0 bytes was read,
since it just returns usb_control_msg() return value. I don't know if
usb_control_msg() can ever return 0, but looks like it's the only
unhanded case

> AX_HOST_EN. Doing a continue means we just ignore the value returned
> by the good read.
>
> I think the correct fix is to look at the value of i. If we have
> exceeded 30, we should return -ETIMEDOUT.
>

Sorry, I don't get how it can help. Report says, that on following line

else if (smsr & AX_HOST_EN)

smsr is uninitialized. How value of i can help here?

Can you, please, explain if you don't mind :)

Thanks


With regards,
Pavel Skripkin

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+f44bad...@syzkaller.appspotmail.com

Tested on:

commit: b0a8b505 kmsan: core: add dependency on DEBUG_KERNEL

git tree: https://github.com/google/kmsan.git master

kernel config: https://syzkaller.appspot.com/x/.config?x=46a956fc7a887c60
dashboard link: https://syzkaller.appspot.com/bug?extid=f44badb06036334e867a
compiler: clang version 14.0.0 (/usr/local/google/src/llvm-git-monorepo 2b554920f11c8b763cd9ed9003f4e19b919b8e1f), GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=163c52a5b00000

Note: testing is done by a robot and is best-effort only.

[Andrew Lunn]

On Sat, Dec 18, 2021 at 05:03:09PM -0800, syzbot wrote:
> Hello,
>
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:
>
> Reported-and-tested-by: syzbot+f44bad...@syzkaller.appspotmail.com

So it looks like you were right. But maybe ret < sizeof(smsr) would be
better?

Andrew

[Pavel Skripkin]

I agree, this looks much cleaner.

Also, the bug you mentioned in previous email is also real, so I will
prepare a patch series if you haven't fixed it by yourself :)



With regards,
Pavel Skripkin