FAILED: patch "[PATCH] ksmbd: reset rcount per connection in" failed to apply to 6.12-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.12-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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x def036ef87f8641c1c525d5ae17438d7a1006491
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026042410-cinch-frostbite-b760@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From def036ef87f8641c1c525d5ae17438d7a1006491 Mon Sep 17 00:00:00 2001
From: DaeMyung Kang <charsyam@gmail.com>
Date: Sun, 19 Apr 2026 02:28:44 +0900
Subject: [PATCH] ksmbd: reset rcount per connection in
 ksmbd_conn_wait_idle_sess_id()

rcount is intended to be connection-specific: 2 for curr_conn, 1 for
every other connection sharing the same session.  However, it is
initialised only once before the hash iteration and is never reset.
After the loop visits curr_conn, later sibling connections are also
checked against rcount == 2, so a sibling with req_running == 1 is
incorrectly treated as idle.  This makes the outcome depend on the
hash iteration order: whether a given sibling is checked against the
loose (< 2) or the strict (< 1) threshold is decided by whether it
happens to be visited before or after curr_conn.

The function's contract is "wait until every connection sharing this
session is idle" so that destroy_previous_session() can safely tear
the session down.  The latched rcount violates that contract and
reopens the teardown race window the wait logic was meant to close:
destroy_previous_session() may proceed before sibling channels have
actually quiesced, overlapping session teardown with in-flight work
on those connections.

Recompute rcount inside the loop so each connection is compared
against its own threshold regardless of iteration order.

This is a code-inspection fix for an iteration-order-dependent logic
error; a targeted reproducer would require SMB3 multichannel with
in-flight work on a sibling channel landing after curr_conn in hash
order, which is not something that can be triggered reliably.

Fixes: 76e98a158b20 ("ksmbd: fix race condition between destroy_previous_session() and smb2 operations()")
Cc: stable@vger.kernel.org
Signed-off-by: DaeMyung Kang <charsyam@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/server/connection.c b/fs/smb/server/connection.c
index a26899d12df1..b5e077f272cf 100644
--- a/fs/smb/server/connection.c
+++ b/fs/smb/server/connection.c
@@ -237,7 +237,7 @@ int ksmbd_conn_wait_idle_sess_id(struct ksmbd_conn *curr_conn, u64 sess_id)
 {
 	struct ksmbd_conn *conn;
 	int rc, retry_count = 0, max_timeout = 120;
-	int rcount = 1, bkt;
+	int rcount, bkt;
 
 retry_idle:
 	if (retry_count >= max_timeout)
@@ -246,8 +246,7 @@ int ksmbd_conn_wait_idle_sess_id(struct ksmbd_conn *curr_conn, u64 sess_id)
 	down_read(&conn_list_lock);
 	hash_for_each(conn_list, bkt, conn, hlist) {
 		if (conn->binding || xa_load(&conn->sessions, sess_id)) {
-			if (conn == curr_conn)
-				rcount = 2;
+			rcount = (conn == curr_conn) ? 2 : 1;
 			if (atomic_read(&conn->req_running) >= rcount) {
 				rc = wait_event_timeout(conn->req_running_q,
 					atomic_read(&conn->req_running) < rcount,