linux-kernel - [PATCH V2 0/2] smb: client: Fix use-after-free in readdir

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Message-ID: <20250516091256.2756826-1-wangzhaolong1@huawei.com>
Date: Fri, 16 May 2025 17:12:54 +0800
From: Wang Zhaolong <wangzhaolong1@...wei.com>
To: <sfrench@...ba.org>, <sfrench@...ibm.com>
CC: <linux-cifs@...r.kernel.org>, <samba-technical@...ts.samba.org>,
	<linux-kernel@...r.kernel.org>, <chengzhihao1@...wei.com>,
	<wangzhaolong1@...wei.com>, <yi.zhang@...wei.com>, <yangerkun@...wei.com>
Subject: [PATCH V2 0/2] smb: client: Fix use-after-free in readdir

V2:
  - Correct spelling mistakes in the commit message, such as 'lopp' -> 'loop'.
  - The titles of patches follow the same style.

This patch series addresses a use-after-free vulnerability in the SMB/CIFS
client readdir implementation that can be triggered during concurrent
directory reads when a signal interrupts directory enumeration.

The root cause is in the operation sequence in find_cifs_entry():
1. When query_dir_next() fails due to signal interruption (ERESTARTSYS)
2. The code continues to access last_entry pointer before checking the return code
3. This can access freed memory since the buffer may have been released

The race condition can be triggered by processes accessing the same directory
with concurrent readdir operations, especially when signals are involved.

The fix is straightforward:
1. First patch ensures we check the return code before using any pointers
2. Second patch improves defensiveness by resetting all related buffer pointers
   when freeing the network buffer

Wang Zhaolong (2):
  smb: client: Fix use-after-free in cifs_fill_dirent
  smb: client: Reset all search buffer pointers when releasing buffer

 fs/smb/client/readdir.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

-- 
2.39.2