Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

mmc: vub300: defer reset until cmd_mutex is unlocked

vub300_cmndwork_thread() holds cmd_mutex while it sends a command and waits for the command response. If the response wait times out, __vub300_command_response() kills the command URBs and then synchronously resets the USB device through usb_reset_device().

That reset path re-enters the driver through vub300_pre_reset(), which also takes cmd_mutex. The worker therefore tries to acquire the same mutex recursively while it is still holding it from the command path.

This issue was found by our static analysis tool and then manually reviewed against the current tree.

The grounded PoC kept the real worker and timeout/reset carrier:

vub300_cmndwork_thread() __vub300_command_response() usb_lock_device_for_reset() usb_reset_device() vub300_pre_reset()

Lockdep reported the same-task recursive acquisition on cmd_mutex:

WARNING: possible recursive locking detected ... (&test_vub300.cmd_mutex) ... at: usb_reset_device... [vuln_msv] ... (&test_vub300.cmd_mutex) ... at: vub300_cmndwork_thread+0x12/0x20 [vuln_msv] Workqueue: vub300_cmd_wq vub300_cmndwork_thread [vuln_msv] *** DEADLOCK ***

Return a flag from __vub300_command_response() when the timeout path needs a device reset, then perform the reset after vub300_cmndwork_thread() has cleared the in-flight command state and dropped cmd_mutex. The reset is still attempted before mmc_request…