FAILED: patch "[PATCH] smb: client: delete compound mids on send failure before" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 8f6f8a48399f82f4a83f7b9f25b9707e0062a4f9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026092900-threefold-unblessed-1235@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 8f6f8a48399f82f4a83f7b9f25b9707e0062a4f9 Mon Sep 17 00:00:00 2001
From: Adarsh Das <adarshdas950@gmail.com>
Date: Sat, 19 Sep 2026 16:27:32 +0530
Subject: [PATCH] smb: client: delete compound mids on send failure before
 unlock

When sending a compound request fails, smb_send_rqst() kicks off a
reconnect. compound_send_recv() still has those mids on pending_mid_q,
but it unlocks the server without removing them first.

During reconnect, cifs_abort_connection() walks pending_mid_q and runs
each mid callback. With no response yet, those callbacks return credits
and drop in_flight. Then compound_send_recv()'s send-error path returns
the same credits again. in_flight ends up decremented twice and
smb2_add_credits() WARNs.

syzbot hits this during SMB2_negotiate when the socket send fails.

cifs_call_async() already calls delete_mid() before unlock on send
failure. Do the same for compound chains and set cancelled_mid[] so the
out: path does not delete them again.

Fixes: ee258d79159a ("CIFS: Move credit processing to mid callbacks for SMB3")
Reported-by: syzbot+eeb58d2197d88720a228@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/6a727d22.40259c87.584f4.04ce.GAE@google.com
Tested-by: syzbot+eeb58d2197d88720a228@syzkaller.appspotmail.com
Assisted-by: LLM
Cc: stable@vger.kernel.org
Signed-off-by: Adarsh Das <adarshdas950@gmail.com>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>

diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
index e266859818a4..7df5b3447aea 100644
--- a/fs/smb/client/transport.c
+++ b/fs/smb/client/transport.c
@@ -965,6 +965,10 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 	if (rc < 0) {
 		revert_current_mid(server, num_rqst);
 		server->sequence_number -= 2;
+		for (i = 0; i < num_rqst; i++) {
+			delete_mid(server, mid[i]);
+			cancelled_mid[i] = true;
+		}
 	}
 
 	cifs_server_unlock(server);