CVE-2026-90162

ksmbd: defer publishing granted locks to prevent UAF/double-free race

Published Sep 17, 2026 CVSS 3.1 · 8.8 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

ksmbd: defer publishing granted locks to prevent UAF/double-free race

In smb2_lock(), mid-batch granted locks are published to connection-wide
(conn->lock_list) and file-wide (fp->lock_list) lists immediately upon
vfs_lock_file() success, while also remaining tracked on the stack-local
rollback_list.

If a subsequent element in the same SMB2_LOCK request array fails
validation or execution, the thread jumps to out: and walks
rollback_list to undo previously granted locks. However, because the
granted lock was already published to conn->lock_list, a concurrent
UNLOCK request on the same connection can find the lock object and
kfree() it before the rollback loop executes.

When the granting thread subsequently walks rollback_list, it
dereferences and frees the already-freed ksmbd_lock structure, resulting
in a Use-After-Free and Double-Free (on both ksmbd_lock and struct
file_lock).

Fix this by deferring the publication of granted locks to
conn->lock_list and fp->lock_list until after the entire array of lock
elements has been processed without error. Mid-batch grants remain
tracked exclusively on the request-local rollback_list until the whole
batch succeeds, eliminating the race window.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4904-1 linux-6.12 security update
Ubuntu USN Ubuntu USN USN-9018-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9018-2 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9091-1 Linux kernel (NVIDIA Tegra) vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-416
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ksmbd: defer publishing granted locks to prevent UAF/double-free race In smb2_lock(), mid-batch granted locks are published to connection-wide (conn->lock_list) and file-wide (fp->lock_list) lists immediately upon vfs_lock_file() success, while also remaining tracked on the stack-local rollback_list. If a subsequent element in the same SMB2_LOCK request array fails validation or execution, the thread jumps to out: and walks rollback_list to undo previously granted locks. However, because the granted lock was already published to conn->lock_list, a concurrent UNLOCK request on the same connection can find the lock object and kfree() it before the rollback loop executes. When the granting thread subsequently walks rollback_list, it dereferences and frees the already-freed ksmbd_lock structure, resulting in a Use-After-Free and Double-Free (on both ksmbd_lock and struct file_lock). Fix this by deferring the publication of granted locks to conn->lock_list and fp->lock_list until after the entire array of lock elements has been processed without error. Mid-batch grants remain tracked exclusively on the request-local rollback_list until the whole batch succeeds, eliminating the race window.
Title ksmbd: defer publishing granted locks to prevent UAF/double-free race
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 30, 2026, 12:34 PM
Reserved
Sep 11, 2026, 7:38 PM
Status
Received
Published
Sep 17, 2026, 5:17 PM
Modified
Oct 30, 2026, 1:20 PM