CVE-2026-80659: mmc: vub300: defer reset until cmd_mutex is unlocked

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

mmc: vub300: defer reset until cmdmutex is unlocked

vub300cmndworkthread() holds cmdmutex while it sends a command and waits for the command response. If the response wait times out, vub300commandresponse() kills the command URBs and then synchronously resets the USB device through usbresetdevice().

That reset path re-enters the driver through vub300prereset(), which also takes cmdmutex. 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:

vub300cmndworkthread() vub300commandresponse() usblockdeviceforreset() usbresetdevice() vub300prereset()

Lockdep reported the same-task recursive acquisition on cmdmutex:

WARNING: possible recursive locking detected ... (&testvub300.cmdmutex) ... at: usbresetdevice... [vulnmsv] ... (&testvub300.cmdmutex) ... at: vub300cmndworkthread+0x12/0x20 [vulnmsv] Workqueue: vub300cmdwq vub300cmndworkthread [vulnmsv] DEADLOCK

Return a flag from vub300commandresponse() when the timeout path needs a device reset, then perform the reset after vub300cmndworkthread() has cleared the in-flight command state and dropped cmdmutex. The reset is still attempted before mmcrequestdone(), preserving the existing request completion ordering while avoiding the recursive lock.