CVE-2026-99039

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

memstick: core: wait for request completion before freeing card

In memstick alloc card() and memstick set rw addr(), wait for completion timeout() is used to wait for device identification and address configuration requests to complete.

The memstick subsystem does not provide an abort or cancellation callback in struct memstick host for in-flight requests. If wait for completion timeout() expires (for instance, when a USB transfer or command retry is delayed), memstick alloc card() returns an error and frees the memstick dev structure via kfree(card).

However, the host controller driver (such as rtsx usb ms) is still running the request asynchronously in worker context. When the transfer eventually finishes, the driver writes into host->req->data, which points to memory inside the already freed card structure. This leads to a KASAN slab-use-after-free write:

BUG: KASAN: slab-use-after-free in ms read bytes+0x8fe/0x990 Write of size 1 at addr ffff88813c188079 by task kworker/1:5/5239 Workqueue: events rtsx usb ms handle req Call Trace: ms read bytes+0x8fe/0x990 drivers/memstick/host/rtsx usb ms.c:450 rtsx usb ms issue cmd drivers/memstick/host/rtsx usb ms.c:477 [inline] rtsx usb ms handle req+0x557/0x1a00 drivers/memstick/host/rtsx usb ms.c:531 process one work+0xac7/0x1b10 kernel/workqueue.c:3396 worker thread+0x5ef/0xe50 kernel/workqueue.c:3560 kthread+0x373/0x450 kernel/kthread.c:436

Allocated by task 1662: memstick alloc card drivers/memstick/core/memstick.c:383 [inline] memstick check+0x2c1/0x10d0 drivers/memstick/core/memstick.c:452 process one work+0xac7/0x1b10 kernel/workqueue.c:3396

Freed by task 1662: kfree+0x20c/0x650 mm/slub.c:6792 memstick alloc card drivers/memstick/core/memstick.c:420 [inline] memstick check+0x72b/0x10d0 drivers/memstick/core/memstick.c:452 process one work+0xac7/0x1b10 kernel/workqueue.c:3396

Host controller drivers (rtsx usb ms, jmb38x ms, tifm ms, r592) already implement their own hardware and bus timeouts, and callers in mspro block and ms block already rely on wait for completion() unconditionally.

Replace wait for completion timeout() with wait for completion() in memstick set rw addr() and memstick alloc card() so that the card structure is never freed while an asynchronous request is in flight.