Bug 2559785 (CVE-2026-99039)

Summary:	CVE-2026-99039 kernel: memstick: core: wait for request completion before freeing card
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's memstick subsystem. This vulnerability allows a local user or physically proximate attacker to cause a Denial of Service (DoS) or kernel memory corruption. When device initialization or configuration requests experience a timeout, the kernel prematurely frees the memory structure associated with the card while asynchronous hardware operations remain active. When the delayed operation completes, the host controller driver writes into the released memory, triggering a use-after-free condition that leads to a system crash.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-23 13:37:11 UTC

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.