Re: [PATCH] net: usb: smsc75xx: Fix uninit-value access in __smsc75xx_read_reg

[Simon Horman]

On Sun, Sep 24, 2023 at 02:35:49AM +0900, Shigeru Yoshida wrote:
> syzbot reported the following uninit-value access issue:
> 
> =====================================================
> BUG: KMSAN: uninit-value in smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:975 [inline]
> BUG: KMSAN: uninit-value in smsc75xx_bind+0x5c9/0x11e0 drivers/net/usb/smsc75xx.c:1482
> CPU: 0 PID: 8696 Comm: kworker/0:3 Not tainted 5.8.0-rc5-syzkaller #0
> 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+0x21c/0x280 lib/dump_stack.c:118
>  kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
>  __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
>  smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:975 [inline]
>  smsc75xx_bind+0x5c9/0x11e0 drivers/net/usb/smsc75xx.c:1482
>  usbnet_probe+0x1152/0x3f90 drivers/net/usb/usbnet.c:1737
>  usb_probe_interface+0xece/0x1550 drivers/usb/core/driver.c:374
>  really_probe+0xf20/0x20b0 drivers/base/dd.c:529
>  driver_probe_device+0x293/0x390 drivers/base/dd.c:701
>  __device_attach_driver+0x63f/0x830 drivers/base/dd.c:807
>  bus_for_each_drv+0x2ca/0x3f0 drivers/base/bus.c:431
>  __device_attach+0x4e2/0x7f0 drivers/base/dd.c:873
>  device_initial_probe+0x4a/0x60 drivers/base/dd.c:920
>  bus_probe_device+0x177/0x3d0 drivers/base/bus.c:491
>  device_add+0x3b0e/0x40d0 drivers/base/core.c:2680
>  usb_set_configuration+0x380f/0x3f10 drivers/usb/core/message.c:2032
>  usb_generic_driver_probe+0x138/0x300 drivers/usb/core/generic.c:241
>  usb_probe_device+0x311/0x490 drivers/usb/core/driver.c:272
>  really_probe+0xf20/0x20b0 drivers/base/dd.c:529
>  driver_probe_device+0x293/0x390 drivers/base/dd.c:701
>  __device_attach_driver+0x63f/0x830 drivers/base/dd.c:807
>  bus_for_each_drv+0x2ca/0x3f0 drivers/base/bus.c:431
>  __device_attach+0x4e2/0x7f0 drivers/base/dd.c:873
>  device_initial_probe+0x4a/0x60 drivers/base/dd.c:920
>  bus_probe_device+0x177/0x3d0 drivers/base/bus.c:491
>  device_add+0x3b0e/0x40d0 drivers/base/core.c:2680
>  usb_new_device+0x1bd4/0x2a30 drivers/usb/core/hub.c:2554
>  hub_port_connect drivers/usb/core/hub.c:5208 [inline]
>  hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
>  port_event drivers/usb/core/hub.c:5494 [inline]
>  hub_event+0x5e7b/0x8a70 drivers/usb/core/hub.c:5576
>  process_one_work+0x1688/0x2140 kernel/workqueue.c:2269
>  worker_thread+0x10bc/0x2730 kernel/workqueue.c:2415
>  kthread+0x551/0x590 kernel/kthread.c:292
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
> 
> Local variable ----buf.i87@smsc75xx_bind created at:
>  __smsc75xx_read_reg drivers/net/usb/smsc75xx.c:83 [inline]
>  smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:968 [inline]
>  smsc75xx_bind+0x485/0x11e0 drivers/net/usb/smsc75xx.c:1482
>  __smsc75xx_read_reg drivers/net/usb/smsc75xx.c:83 [inline]
>  smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:968 [inline]
>  smsc75xx_bind+0x485/0x11e0 drivers/net/usb/smsc75xx.c:1482
> 
> This issue is caused because usbnet_read_cmd() reads less bytes than requested
> (zero byte in the reproducer). In this case, 'buf' is not properly filled.
> 
> This patch fixes the issue by returning -ENODATA if usbnet_read_cmd() reads
> less bytes than requested.
> 
> Fixes: d0cad871703b ("smsc75xx: SMSC LAN75xx USB gigabit ethernet adapter driver")
> Reported-and-tested-by: syzbot+6966546b78d050bb0b5d@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=6966546b78d050bb0b5d
> Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>

Reviewed-by: Simon Horman <horms@xxxxxxxxxx>