Bug 2568631 (CVE-2026-99276)

Summary:	CVE-2026-99276 kernel: kernel: Denial of Service in ksmbd via deadlock during session cleanup
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 ksmbd (Server Message Block) server. A remote client can cause a Denial of Service (DoS) by triggering a deadlock condition during concurrent session teardown and connection cleanup operations. Because the periodic connection cleanup worker and session termination routines acquire internal locks in conflicting orders, simultaneous requests can become permanently blocked, causing the server to hang.	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 2026-11-07 14:22:11 UTC

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

ksmbd: defer connection scavenging while session locks are busy

The expiration worker holds conn_list_lock for reading while checking
for authenticated sessions. Without this change, the check can wait for
conn->session_lock or sessions_table_lock.

In destroy_previous_session(), the status updates after
ksmbd_conn_wait_idle_sess() run with both session locks held for
writing. Both the KSMBD_SESS_GOOD error path and the
KSMBD_SESS_NEED_SETUP success path call ksmbd_all_conn_set_status(),
which takes conn_list_lock for reading.

A writer queued on conn_list_lock can block these new read acquisitions.
The worker then waits for a session lock held by
destroy_previous_session(), which waits behind the writer. The writer
cannot proceed until the worker releases conn_list_lock.

Try both session locks instead of waiting in the scavenging check. Keep
the connection when either lock is busy and let the periodic worker
retry later.