From 4f3a06cc57976cafa8c6f716646be6c79a99e485 Mon Sep 17 00:00:00 2001 From: Namjae Jeon Date: Mon, 9 Feb 2026 10:43:19 +0900 Subject: [PATCH] ksmbd: add chann_lock to protect ksmbd_chann_list xarray ksmbd_chann_list xarray lacks synchronization, allowing use-after-free in multi-channel sessions (between lookup_chann_list() and ksmbd_chann_del). Adds rw_semaphore chann_lock to struct ksmbd_session and protects all xa_load/xa_store/xa_erase accesses. Cc: stable@vger.kernel.org Reported-by: Igor Stepansky Signed-off-by: Namjae Jeon Signed-off-by: Steve French --- fs/smb/server/mgmt/user_session.c | 5 +++++ fs/smb/server/mgmt/user_session.h | 1 + fs/smb/server/smb2pdu.c | 12 +++++++++++- 3 files changed, 17 insertions(+), 1 deletion(-) diff --git a/fs/smb/server/mgmt/user_session.c b/fs/smb/server/mgmt/user_session.c index 68b3e0cb54d38..8c2b14ea7b0ec 100644 --- a/fs/smb/server/mgmt/user_session.c +++ b/fs/smb/server/mgmt/user_session.c @@ -244,12 +244,14 @@ static void free_channel_list(struct ksmbd_session *sess) struct channel *chann; unsigned long index; + down_write(&sess->chann_lock); xa_for_each(&sess->ksmbd_chann_list, index, chann) { xa_erase(&sess->ksmbd_chann_list, index); kfree(chann); } xa_destroy(&sess->ksmbd_chann_list); + up_write(&sess->chann_lock); } static void __session_rpc_close(struct ksmbd_session *sess, @@ -434,7 +436,9 @@ static int ksmbd_chann_del(struct ksmbd_conn *conn, struct ksmbd_session *sess) { struct channel *chann; + down_write(&sess->chann_lock); chann = xa_erase(&sess->ksmbd_chann_list, (long)conn); + up_write(&sess->chann_lock); if (!chann) return -ENOENT; @@ -668,6 +672,7 @@ static struct ksmbd_session *__session_create(int protocol) rwlock_init(&sess->tree_conns_lock); atomic_set(&sess->refcnt, 2); init_rwsem(&sess->rpc_lock); + init_rwsem(&sess->chann_lock); ret = __init_smb2_session(sess); if (ret) diff --git a/fs/smb/server/mgmt/user_session.h b/fs/smb/server/mgmt/user_session.h index 176d800c24906..d94f5e128a9b4 100644 --- a/fs/smb/server/mgmt/user_session.h +++ b/fs/smb/server/mgmt/user_session.h @@ -48,6 +48,7 @@ struct ksmbd_session { char sess_key[CIFS_KEY_SIZE]; struct hlist_node hlist; + struct rw_semaphore chann_lock; struct xarray ksmbd_chann_list; struct xarray tree_conns; struct ida tree_conn_ida; diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 4d3154cc493ea..3efcc7da1b9f6 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -80,7 +80,13 @@ static inline bool check_session_id(struct ksmbd_conn *conn, u64 id) struct channel *lookup_chann_list(struct ksmbd_session *sess, struct ksmbd_conn *conn) { - return xa_load(&sess->ksmbd_chann_list, (long)conn); + struct channel *chann; + + down_read(&sess->chann_lock); + chann = xa_load(&sess->ksmbd_chann_list, (long)conn); + up_read(&sess->chann_lock); + + return chann; } /** @@ -1559,8 +1565,10 @@ binding_session: return -ENOMEM; chann->conn = conn; + down_write(&sess->chann_lock); old = xa_store(&sess->ksmbd_chann_list, (long)conn, chann, KSMBD_DEFAULT_GFP); + up_write(&sess->chann_lock); if (xa_is_err(old)) { kfree(chann); return xa_err(old); @@ -1652,8 +1660,10 @@ binding_session: return -ENOMEM; chann->conn = conn; + down_write(&sess->chann_lock); old = xa_store(&sess->ksmbd_chann_list, (long)conn, chann, KSMBD_DEFAULT_GFP); + up_write(&sess->chann_lock); if (xa_is_err(old)) { kfree(chann); return xa_err(old); -- 2.47.3