[PATCH 6.11 089/184] ksmbd: fix slab-use-after-free in ksmbd_smb2_session_create

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6.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Namjae Jeon <linkinjeon@xxxxxxxxxx>

commit 0a77715db22611df50b178374c51e2ba0d58866e upstream.

There is a race condition between ksmbd_smb2_session_create and
ksmbd_expire_session. This patch add missing sessions_table_lock
while adding/deleting session from global session table.

Cc: stable@xxxxxxxxxxxxxxx # v5.15+
Reported-by: Norbert Szetei <norbert@xxxxxxxxxxxx>
Tested-by: Norbert Szetei <norbert@xxxxxxxxxxxx>
Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/smb/server/mgmt/user_session.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/smb/server/mgmt/user_session.c
+++ b/fs/smb/server/mgmt/user_session.c
@@ -175,6 +175,7 @@ static void ksmbd_expire_session(struct
 	unsigned long id;
 	struct ksmbd_session *sess;
 
+	down_write(&sessions_table_lock);
 	down_write(&conn->session_lock);
 	xa_for_each(&conn->sessions, id, sess) {
 		if (atomic_read(&sess->refcnt) == 0 &&
@@ -188,6 +189,7 @@ static void ksmbd_expire_session(struct
 		}
 	}
 	up_write(&conn->session_lock);
+	up_write(&sessions_table_lock);
 }
 
 int ksmbd_session_register(struct ksmbd_conn *conn,
@@ -229,7 +231,6 @@ void ksmbd_sessions_deregister(struct ks
 			}
 		}
 	}
-	up_write(&sessions_table_lock);
 
 	down_write(&conn->session_lock);
 	xa_for_each(&conn->sessions, id, sess) {
@@ -249,6 +250,7 @@ void ksmbd_sessions_deregister(struct ks
 		}
 	}
 	up_write(&conn->session_lock);
+	up_write(&sessions_table_lock);
 }
 
 struct ksmbd_session *ksmbd_session_lookup(struct ksmbd_conn *conn,






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