[PATCH 5.15 568/570] ksmbd: Fix dangling pointer in krb_authenticate

Greg Kroah-Hartman
2026-04-13T16:42:31Z

From: Sean Heelan <seanheelan@gmail.com>

[ Upstream commit 1e440d5b25b7efccb3defe542a73c51005799a5f ]

krb_authenticate frees sess->user and does not set the pointer
to NULL. It calls ksmbd_krb5_authenticate to reinitialise
sess->user but that function may return without doing so. If
that happens then smb2_sess_setup, which calls krb_authenticate,
will be accessing free'd memory when it later uses sess->user.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Heelan <seanheelan@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Leon Chen <leonchen.oss@139.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ksmbd/smb2pdu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -1619,8 +1619,10 @@ static int krb5_authenticate(struct ksmb
if (prev_sess_id && prev_sess_id != sess->id)
destroy_previous_session(conn, sess->user, prev_sess_id);

- if (sess->state == SMB2_SESSION_VALID)
+ if (sess->state == SMB2_SESSION_VALID) {
ksmbd_free_user(sess->user);
+ sess->user = NULL;
+ }

retval = ksmbd_krb5_authenticate(sess, in_blob, in_len,
out_blob, &out_len);