CVE-2026-43379: ksmbd: fix use-after-free in smb_lazy_parent_lease_break_close()

CVE-2026-43379: ksmbd: fix use-after-free in smb_lazy_parent_lease_break_close()

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

ksmbd: fix use-after-free in smb_lazy_parent_lease_break_close()

opinfo pointer obtained via rcu_dereference(fp->f_opinfo) is being
accessed after rcu_read_unlock() has been called. This creates a
race condition where the memory could be freed by a concurrent
writer between the unlock and the subsequent pointer dereferences
(opinfo->is_lease, etc.), leading to a use-after-free.

The Linux kernel CVE team has assigned CVE-2026-43379 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.6.32 with commit 27b40b7bfcd121fe13a150ffe11957630cf49246 and fixed in 6.6.130 with commit bf4d66d72e4a9e268c1012c331ce9eaedb5e2086
	Issue introduced in 6.9 with commit 5fb282ba4fef8985a5acf2b32681f2ec07732561 and fixed in 6.12.78 with commit 960699317d39f46611f4ebeb69edc567c1f4e6b6
	Issue introduced in 6.9 with commit 5fb282ba4fef8985a5acf2b32681f2ec07732561 and fixed in 6.18.19 with commit dbbd328cf58261ca239756fe1c0d10c9518d3399
	Issue introduced in 6.9 with commit 5fb282ba4fef8985a5acf2b32681f2ec07732561 and fixed in 6.19.9 with commit b3568347c51c46e2cabc356bc34676df98296619
	Issue introduced in 6.9 with commit 5fb282ba4fef8985a5acf2b32681f2ec07732561 and fixed in 7.0 with commit eac3361e3d5dd8067b3258c69615888eb45e9f25

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-43379
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/smb/server/oplock.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/bf4d66d72e4a9e268c1012c331ce9eaedb5e2086
	https://git.kernel.org/stable/c/960699317d39f46611f4ebeb69edc567c1f4e6b6
	https://git.kernel.org/stable/c/dbbd328cf58261ca239756fe1c0d10c9518d3399
	https://git.kernel.org/stable/c/b3568347c51c46e2cabc356bc34676df98296619
	https://git.kernel.org/stable/c/eac3361e3d5dd8067b3258c69615888eb45e9f25