linux-kernel - [PATCH 6.1] ksmbd: fix use-after-free in session logoff

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Message-ID: <20251127150512.106552-1-nkalashnikov@astralinux.ru>
Date: Thu, 27 Nov 2025 18:05:10 +0300
From: Nazar Kalashnikov <sivartiwe@...il.com>
To: stable@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Nazar Kalashnikov <sivartiwe@...il.com>,
	Namjae Jeon <linkinjeon@...nel.org>,
	Steve French <sfrench@...ba.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Tom Talpey <tom@...pey.com>,
	linux-cifs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org,
	Sean Heelan <seanheelan@...il.com>,
	Steve French <stfrench@...rosoft.com>
Subject: [PATCH 6.1] ksmbd: fix use-after-free in session logoff

From: Nazar Kalashnikov <sivartiwe@...il.com>

From: Sean Heelan <seanheelan@...il.com>

commit 2fc9feff45d92a92cd5f96487655d5be23fb7e2b upstream.

The sess->user object can currently be in use by another thread, for
example if another connection has sent a session setup request to
bind to the session being free'd. The handler for that connection could
be in the smb2_sess_setup function which makes use of sess->user.

Signed-off-by: Sean Heelan <seanheelan@...il.com>
Acked-by: Namjae Jeon <linkinjeon@...nel.org>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Nazar Kalashnikov <sivartiwe@...il.com>
---
Backport fix for CVE-2025-37899
 fs/smb/server/smb2pdu.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index d2dca5d2f17c..f72ef3fe4968 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -2252,10 +2252,6 @@ int smb2_session_logoff(struct ksmbd_work *work)
 	sess->state = SMB2_SESSION_EXPIRED;
 	up_write(&conn->session_lock);
 
-	if (sess->user) {
-		ksmbd_free_user(sess->user);
-		sess->user = NULL;
-	}
 	ksmbd_all_conn_set_status(sess_id, KSMBD_SESS_NEED_NEGOTIATE);
 
 	rsp->StructureSize = cpu_to_le16(4);
-- 
2.39.2