Re: KMSAN: uninit-value in mii_nway_restart

(adding the original recipients back)

On Fri, Aug 26, 2022 at 10:44 AM Alexander Potapenko [off-list ref] wrote:

On Tuesday, June 4, 2019 at 12:32:05 PM UTC+2 syzbot wrote:

quoted

Hello,

syzbot found the following crash on:

HEAD commit: f75e4cfe kmsan: use kmsan_handle_urb() in urb.c
git tree: kmsan
console output: https://syzkaller.appspot.com/x/log.txt?x=1180360ea00000
kernel config: https://syzkaller.appspot.com/x/.config?x=602468164ccdc30a
dashboard link: https://syzkaller.appspot.com/bug?extid=1f53a30781af65d2c955
compiler: clang version 9.0.0 (/home/glider/llvm/clang
06d00afa61eef8f7f501ebdb4e8612ea43ec2d78)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16a2b4f2a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=107f4e86a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1f53a3...@syzkaller.appspotmail.com

ax88179_178a 1-1:0.186 (unnamed net_device) (uninitialized): Failed to
write reg index 0x000d: -71
ax88179_178a 1-1:0.186 (unnamed net_device) (uninitialized): Failed to
write reg index 0x000e: -71
ax88179_178a 1-1:0.186 (unnamed net_device) (uninitialized): Failed to
write reg index 0x000d: -71
ax88179_178a 1-1:0.186 (unnamed net_device) (uninitialized): Failed to
write reg index 0x000e: -71
ax88179_178a 1-1:0.186 (unnamed net_device) (uninitialized): Failed to read
reg index 0x0000: -71
==================================================================
BUG: KMSAN: uninit-value in mii_nway_restart+0x141/0x260
drivers/net/mii.c:467
CPU: 1 PID: 3353 Comm: kworker/1:2 Not tainted 5.1.0+ #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x191/0x1f0 lib/dump_stack.c:113
kmsan_report+0x130/0x2a0 mm/kmsan/kmsan.c:622
__msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:310
mii_nway_restart+0x141/0x260 drivers/net/mii.c:467
ax88179_bind+0xee3/0x1a10 drivers/net/usb/ax88179_178a.c:1329
usbnet_probe+0x10f5/0x3940 drivers/net/usb/usbnet.c:1728
usb_probe_interface+0xd66/0x1320 drivers/usb/core/driver.c:361
really_probe+0xdae/0x1d80 drivers/base/dd.c:513
driver_probe_device+0x1b3/0x4f0 drivers/base/dd.c:671
__device_attach_driver+0x5b8/0x790 drivers/base/dd.c:778
bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
__device_attach+0x454/0x730 drivers/base/dd.c:844
device_initial_probe+0x4a/0x60 drivers/base/dd.c:891
bus_probe_device+0x137/0x390 drivers/base/bus.c:514
device_add+0x288d/0x30e0 drivers/base/core.c:2106
usb_set_configuration+0x30dc/0x3750 drivers/usb/core/message.c:2027
generic_probe+0xe7/0x280 drivers/usb/core/generic.c:210
usb_probe_device+0x14c/0x200 drivers/usb/core/driver.c:266
really_probe+0xdae/0x1d80 drivers/base/dd.c:513
driver_probe_device+0x1b3/0x4f0 drivers/base/dd.c:671
__device_attach_driver+0x5b8/0x790 drivers/base/dd.c:778
bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
__device_attach+0x454/0x730 drivers/base/dd.c:844
device_initial_probe+0x4a/0x60 drivers/base/dd.c:891
bus_probe_device+0x137/0x390 drivers/base/bus.c:514
device_add+0x288d/0x30e0 drivers/base/core.c:2106
usb_new_device+0x23e5/0x2ff0 drivers/usb/core/hub.c:2534
hub_port_connect drivers/usb/core/hub.c:5089 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
port_event drivers/usb/core/hub.c:5350 [inline]
hub_event+0x48d1/0x7290 drivers/usb/core/hub.c:5432
process_one_work+0x1572/0x1f00 kernel/workqueue.c:2269
worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
kthread+0x4b5/0x4f0 kernel/kthread.c:254
ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Local variable description: ----buf.i@ax88179_mdio_read
Variable was created at:
__ax88179_read_cmd drivers/net/usb/ax88179_178a.c:199 [inline]
ax88179_read_cmd drivers/net/usb/ax88179_178a.c:311 [inline]
ax88179_mdio_read+0x7b/0x240 drivers/net/usb/ax88179_178a.c:369
mii_nway_restart+0xcf/0x260 drivers/net/mii.c:465
==================================================================

quoted

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot can test patches for this bug, for details see:
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This bug is still triggerable by KMSAN (https://syzkaller.appspot.com/bug?id=835562bfa4dd92c72f323f29ad388c9cb4b0e63f):

=====================================================
BUG: KMSAN: uninit-value in mii_nway_restart+0x117/0x1d0 drivers/net/mii.c:465
 mii_nway_restart+0x117/0x1d0 drivers/net/mii.c:465
 dm9601_bind+0xa17/0xb50 drivers/net/usb/dm9601.c:431
 usbnet_probe+0xebb/0x3cc0 drivers/net/usb/usbnet.c:1747
 usb_probe_interface+0xc4b/0x11f0 drivers/usb/core/driver.c:396
 really_probe+0x499/0xf50 drivers/base/dd.c:634
 __driver_probe_device+0x2fa/0x3d0 drivers/base/dd.c:764
 driver_probe_device+0x72/0x7a0 drivers/base/dd.c:794
 __device_attach_driver+0x6f1/0x890 drivers/base/dd.c:917
 bus_for_each_drv+0x1fc/0x360 drivers/base/bus.c:427
 __device_attach+0x42a/0x720 drivers/base/dd.c:989
 device_initial_probe+0x2e/0x40 drivers/base/dd.c:1038
 bus_probe_device+0x13c/0x3b0 drivers/base/bus.c:487
 device_add+0x1d4b/0x26c0 drivers/base/core.c:3428
 usb_set_configuration+0x30f8/0x37e0 drivers/usb/core/message.c:2170
 usb_generic_driver_probe+0x105/0x290 drivers/usb/core/generic.c:238
 usb_probe_device+0x288/0x490 drivers/usb/core/driver.c:293
 really_probe+0x499/0xf50 drivers/base/dd.c:634
 __driver_probe_device+0x2fa/0x3d0 drivers/base/dd.c:764
 driver_probe_device+0x72/0x7a0 drivers/base/dd.c:794
 __device_attach_driver+0x6f1/0x890 drivers/base/dd.c:917
 bus_for_each_drv+0x1fc/0x360 drivers/base/bus.c:427
 __device_attach+0x42a/0x720 drivers/base/dd.c:989
 device_initial_probe+0x2e/0x40 drivers/base/dd.c:1038
 bus_probe_device+0x13c/0x3b0 drivers/base/bus.c:487
 device_add+0x1d4b/0x26c0 drivers/base/core.c:3428
 usb_new_device+0x17a1/0x2360 drivers/usb/core/hub.c:2566
 hub_port_connect drivers/usb/core/hub.c:5363 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5507 [inline]
 port_event drivers/usb/core/hub.c:5663 [inline]
 hub_event+0x5559/0x8050 drivers/usb/core/hub.c:5745
 process_one_work+0xb27/0x13e0 kernel/workqueue.c:2289
 worker_thread+0x1076/0x1d60 kernel/workqueue.c:2436
 kthread+0x31b/0x430 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

Local variable res created at:
 dm9601_mdio_read+0x49/0xf0 drivers/net/usb/dm9601.c:226
 mii_nway_restart+0x84/0x1d0 drivers/net/mii.c:463

CPU: 0 PID: 28 Comm: kworker/0:1 Not tainted 5.19.0-syzkaller-32655-g1b070a5d1a2c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Workqueue: usb_hub_wq hub_event
=====================================================

I believe we should either be always checking the return value of dm_read_shared_word(), or make it unconditionally initialize *value.

-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

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