[PATCH] ksmbd: scope conn->binding slowpath to bound sessions only

[PATCH] ksmbd: scope conn->binding slowpath to bound sessions only

[Hyunwoo Kim]

When the binding SESSION_SETUP sets conn->binding = true, the flag stays
set after the call so that the global session lookup in
ksmbd_session_lookup_all() can find the session, which was not added to
conn->sessions. Because the flag is connection-wide, the global lookup
path will also resolve any other session by id if asked.

Tighten the global lookup so that the returned session must have this
connection registered in its channel xarray (sess->ksmbd_chann_list).
The channel entry is installed by the existing binding_session path in
ntlm_authenticate()/krb5_authenticate() when a SESSION_SETUP completes
successfully, so this condition is a strict equivalent of "this
connection has been accepted as a channel of this session". Connections
that have not bound to a given session cannot reach it via the global
table.

The existing conn->binding gate for entering the slowpath is preserved
so that non-binding connections keep the fast-path-only behavior, and
the session->state check is unchanged.

Fixes: f5a544e3bab7 ("ksmbd: add support for SMB3 multichannel")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
 fs/smb/server/mgmt/user_session.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/smb/server/mgmt/user_session.c b/fs/smb/server/mgmt/user_session.c
index a86589408835..ab8852da76f0 100644
--- a/fs/smb/server/mgmt/user_session.c
+++ b/fs/smb/server/mgmt/user_session.c
@@ -547,8 +547,13 @@ struct ksmbd_session *ksmbd_session_lookup_all(struct ksmbd_conn *conn,
 	struct ksmbd_session *sess;
 
 	sess = ksmbd_session_lookup(conn, id);
-	if (!sess && conn->binding)
+	if (!sess && conn->binding) {
 		sess = ksmbd_session_lookup_slowpath(id);
+		if (sess && !xa_load(&sess->ksmbd_chann_list, (long)conn)) {
+			ksmbd_user_session_put(sess);
+			sess = NULL;
+		}
+	}
 	if (sess && sess->state != SMB2_SESSION_VALID) {
 		ksmbd_user_session_put(sess);
 		sess = NULL;
-- 
2.43.0

Re: [PATCH] ksmbd: scope conn->binding slowpath to bound sessions only

[Namjae Jeon]

On Tue, Apr 21, 2026 at 12:31 AM Hyunwoo Kim <imv4bel@gmail.com> wrote:
>
> When the binding SESSION_SETUP sets conn->binding = true, the flag stays
> set after the call so that the global session lookup in
> ksmbd_session_lookup_all() can find the session, which was not added to
> conn->sessions. Because the flag is connection-wide, the global lookup
> path will also resolve any other session by id if asked.
>
> Tighten the global lookup so that the returned session must have this
> connection registered in its channel xarray (sess->ksmbd_chann_list).
> The channel entry is installed by the existing binding_session path in
> ntlm_authenticate()/krb5_authenticate() when a SESSION_SETUP completes
> successfully, so this condition is a strict equivalent of "this
> connection has been accepted as a channel of this session". Connections
> that have not bound to a given session cannot reach it via the global
> table.
>
> The existing conn->binding gate for entering the slowpath is preserved
> so that non-binding connections keep the fast-path-only behavior, and
> the session->state check is unchanged.
>
> Fixes: f5a544e3bab7 ("ksmbd: add support for SMB3 multichannel")
> Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Applied it to #ksmbd-for-next-next.
Thanks!