linux-kernel - [PATCH] ksmbd: fix leak of transform buffer on encrypt

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Message-Id: <20251104141214.345175-1-pioooooooooip@gmail.com>
Date: Tue,  4 Nov 2025 23:12:14 +0900
From: Qianchang Zhao <pioooooooooip@...il.com>
To: Namjae Jeon <linkinjeon@...nel.org>,
	Steve French <smfrench@...il.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Tom Talpey <tom@...pey.com>,
	linux-cifs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org,
	Qianchang Zhao <pioooooooooip@...il.com>,
	Zhitong Liu <liuzhitong1993@...il.com>,
	stable@...r.kernel.org
Subject: [PATCH] ksmbd: fix leak of transform buffer on encrypt_resp() failure

When encrypt_resp() fails at the send path, we only set
STATUS_DATA_ERROR but leave the transform buffer allocated (work->tr_buf
in this tree). Repeating this path leaks kernel memory and can lead to
OOM (DoS) when encryption is required.

Reproduced on: Linux v6.18-rc2 (self-built test kernel)

Fix by freeing the transform buffer and forcing plaintext error reply.

Reported-by: Qianchang Zhao <pioooooooooip@...il.com>
Reported-by: Zhitong Liu <liuzhitong1993@...il.com>
Cc: stable@...r.kernel.org
Signed-off-by: Qianchang Zhao <pioooooooooip@...il.com>
---
 fs/smb/server/server.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/smb/server/server.c b/fs/smb/server/server.c
index 40420544c..15dd13e76 100644
--- a/fs/smb/server/server.c
+++ b/fs/smb/server/server.c
@@ -244,8 +244,14 @@ static void __handle_ksmbd_work(struct ksmbd_work *work,
 	if (work->sess && work->sess->enc && work->encrypted &&
 	    conn->ops->encrypt_resp) {
 		rc = conn->ops->encrypt_resp(work);
-		if (rc < 0)
+		if (rc < 0) {
 			conn->ops->set_rsp_status(work, STATUS_DATA_ERROR);
+			work->encrypted = false;
+			if (work->tr_buf) {
+				kvfree(work->tr_buf);
+				work->tr_buf = NULL;
+			}
+		}
 	}
 	if (work->sess)
 		ksmbd_user_session_put(work->sess);
-- 
2.34.1