linux-cve-announce - CVE-2025-40268: cifs: client: fix memory leak in smb3_fs_context_parse

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Message-ID: <2025120715-CVE-2025-40268-390a@gregkh>
Date: Sun,  7 Dec 2025 06:52:15 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40268: cifs: client: fix memory leak in smb3_fs_context_parse_param

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

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

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

cifs: client: fix memory leak in smb3_fs_context_parse_param

The user calls fsconfig twice, but when the program exits, free() only
frees ctx->source for the second fsconfig, not the first.
Regarding fc->source, there is no code in the fs context related to its
memory reclamation.

To fix this memory leak, release the source memory corresponding to ctx
or fc before each parsing.

syzbot reported:
BUG: memory leak
unreferenced object 0xffff888128afa360 (size 96):
  backtrace (crc 79c9c7ba):
    kstrdup+0x3c/0x80 mm/util.c:84
    smb3_fs_context_parse_param+0x229b/0x36c0 fs/smb/client/fs_context.c:1444

BUG: memory leak
unreferenced object 0xffff888112c7d900 (size 96):
  backtrace (crc 79c9c7ba):
    smb3_fs_context_fullpath+0x70/0x1b0 fs/smb/client/fs_context.c:629
    smb3_fs_context_parse_param+0x2266/0x36c0 fs/smb/client/fs_context.c:1438

The Linux kernel CVE team has assigned CVE-2025-40268 to this issue.


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

	Fixed in 6.6.117 with commit 868fc62811d3fabcf5685e14f36377a855d5412d
	Fixed in 6.12.59 with commit 48c17341577e25a22feb13d694374b61d974edbc
	Fixed in 6.17.9 with commit 4515743cc7a42e1d67468402a6420c195532a6fa
	Fixed in 6.18 with commit e8c73eb7db0a498cd4b22d2819e6ab1a6f506bd6

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-2025-40268
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/client/fs_context.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/868fc62811d3fabcf5685e14f36377a855d5412d
	https://git.kernel.org/stable/c/48c17341577e25a22feb13d694374b61d974edbc
	https://git.kernel.org/stable/c/4515743cc7a42e1d67468402a6420c195532a6fa
	https://git.kernel.org/stable/c/e8c73eb7db0a498cd4b22d2819e6ab1a6f506bd6