Bug 2559777 (CVE-2026-99035)

Summary:	CVE-2026-99035 kernel: mmc: mtk-sd: Cancel request timeout work on remove
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 MediaTek SD/MMC host controller driver within the Linux kernel. When the driver is removed or unbound, it fails to wait for active request timeout tasks to complete before releasing host memory resources. A local user could exploit this timing issue during device removal to trigger a use-after-free condition, leading to a denial of service (DoS) or kernel memory corruption.	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 13:35:15 UTC

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

mmc: mtk-sd: Cancel request timeout work on remove

The driver queues req_timeout while a request is active.
msdc_request_done() uses cancel_delayed_work(), which does not wait for
a timeout callback that has already started.

The timeout callback calls mmc_request_done(), which wakes the request
waiter, and then continues to use host->dev_comp and check the SDIO IRQ.
During unbind, msdc_drv_remove() can return and the managed mmc_host can
be freed before the callback finishes.

KASAN reported use-after-free accesses in msdc_request_done() and
msdc_recheck_sdio_irq() in each of three unbind tests.  The same tests
completed without a kernel diagnostic after this change.

Call cancel_delayed_work_sync() after mmc_remove_host() has stopped new
requests and before the driver releases the host resources.

Comment 1 gkamathe 2026-10-27 14:03:55 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-99035.mbox