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

ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()

smb_grant_oplock() has two issues in the oplock publication sequence:

1) opinfo is linked into ci->m_op_list (via opinfo_add) before
add_lease_global_list() is called. If add_lease_global_list()
fails (kmalloc returns NULL), the error path frees the opinfo
via __free_opinfo() while it is still linked in ci->m_op_list.
Concurrent m_op_list readers (opinfo_get_list, or direct iteration
in smb_break_all_levII_oplock) dereference the freed node.

2) opinfo->o_fp is assigned after add_lease_global_list() publishes
the opinfo on the global lease list. A concurrent
find_same_lease_key() can walk the lease list and dereference
opinfo->o_fp->f_ci while o_fp is still NULL.

Fix by restructuring the publication sequence to eliminate post-publish
failure:

- Set opinfo->o_fp before any list publication (fixes NULL deref).
- Preallocate lease_table via alloc_lease_table() before opinfo_add()
so add_lease_global_list() becomes infallible after publication.
- Keep the original m_op_list publication order (opinfo_add before
lease list) so concurrent opens via same_client_has_lease() and
opinfo_get_list() still see the in-flight grant.
- Use opinfo_put() instead of __free_opinfo() on err_out so that
the RCU-deferred free path is used.

This also requires splitting add_lease_global_list() to take a
preallocated lease_table and changing its return type from int to void,
since it can no longer fail.
Published: 2026-04-22
Score: n/a
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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History

Thu, 23 Apr 2026 00:15:00 +0000


Wed, 22 Apr 2026 14:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free and NULL deref in smb_grant_oplock() smb_grant_oplock() has two issues in the oplock publication sequence: 1) opinfo is linked into ci->m_op_list (via opinfo_add) before add_lease_global_list() is called. If add_lease_global_list() fails (kmalloc returns NULL), the error path frees the opinfo via __free_opinfo() while it is still linked in ci->m_op_list. Concurrent m_op_list readers (opinfo_get_list, or direct iteration in smb_break_all_levII_oplock) dereference the freed node. 2) opinfo->o_fp is assigned after add_lease_global_list() publishes the opinfo on the global lease list. A concurrent find_same_lease_key() can walk the lease list and dereference opinfo->o_fp->f_ci while o_fp is still NULL. Fix by restructuring the publication sequence to eliminate post-publish failure: - Set opinfo->o_fp before any list publication (fixes NULL deref). - Preallocate lease_table via alloc_lease_table() before opinfo_add() so add_lease_global_list() becomes infallible after publication. - Keep the original m_op_list publication order (opinfo_add before lease list) so concurrent opens via same_client_has_lease() and opinfo_get_list() still see the in-flight grant. - Use opinfo_put() instead of __free_opinfo() on err_out so that the RCU-deferred free path is used. This also requires splitting add_lease_global_list() to take a preallocated lease_table and changing its return type from int to void, since it can no longer fail.
Title ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

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Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-04-22T13:53:41.351Z

Reserved: 2026-03-09T15:48:24.090Z

Link: CVE-2026-31444

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-04-22T14:16:38.010

Modified: 2026-04-23T16:17:41.280

Link: CVE-2026-31444

cve-icon Redhat

Severity :

Publid Date: 2026-04-22T00:00:00Z

Links: CVE-2026-31444 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-04-22T15:45:20Z

Weaknesses