Subject: FAILED: patch "[PATCH] smb: client: cancel reconnect work in" failed to apply to 6.1-stable tree
To: pc@manguebit.org,bharathsm@microsoft.com,dhowells@redhat.com,linkinjeon@kernel.org,ronniesahlberg@gmail.com,sprasad@microsoft.com,tom@talpey.com
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Tue, 22 Sep 2026 17:04:59 +0200
Message-ID: <2026092259-extortion-dragging-26e2@gregkh>
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The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x c65eae6f61d1778ff7a82e4aae4080e26f486af1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026092259-extortion-dragging-26e2@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:


thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c65eae6f61d1778ff7a82e4aae4080e26f486af1 Mon Sep 17 00:00:00 2001
From: Paulo Alcantara <pc@manguebit.org>
Date: Fri, 11 Sep 2026 22:38:04 -0300
Subject: [PATCH] smb: client: cancel reconnect work in
 clean_demultiplex_info()

clean_demultiplex_info() cancels server->echo delayed work but not
server->reconnect, which can cause a use-after-free when the
demultiplex thread exits while a reconnect work is still queued:

  cifs_demultiplex_thread()
    cifs_readv_from_socket()
      cifs_reconnect()
        __cifs_reconnect()
          cifs_queue_server_reconn()
            mod_delayed_work(cifsiod_wq, &server->reconnect, 0)
    clean_demultiplex_info()
      cancel_delayed_work_sync(&server->echo)   // echo canceled
                                                 // reconnect NOT canceled
      kfree_sensitive(server)                    // server freed

  ...later, on cifsiod_wq:

  smb2_reconnect_server()
    server->srv_count  // UAF read of freed server

Fix this by canceling server->reconnect delayed work in
clean_demultiplex_info() before the server is freed, the same way
cifs_put_tcp_session() already does.

Reported-by: syzbot+5003556314abc915a71f@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/6aa4a12d.f81106d8.2ab401.0023.GAE@google.com
Fixes: 53e0e11efe92 ("CIFS: Fix a possible memory corruption during reconnect")
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: stable@vger.kernel.org

diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index b6e98eb31673..bef710d9a3c3 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -1067,6 +1067,7 @@ clean_demultiplex_info(struct TCP_Server_Info *server)
 	spin_unlock(&server->srv_lock);
 
 	cancel_delayed_work_sync(&server->echo);
+	cancel_delayed_work_sync(&server->reconnect);
 
 	spin_lock(&server->srv_lock);
 	server->tcpStatus = CifsExiting;