TCP_Server_Info.rlist is allocated via kzalloc which zeros both ->next and ->prev to NULL instead of pointing to itself, making list_empty() always return false and list_add() dereference a NULL ->prev pointer. Also, cifs_signal_cifsd_for_reconnect() can be called concurrently from multiple cifsd threads, allowing the same server's rlist node to be added twice into the local list, corrupting it. Closes: https://sashiko.dev/#/patchset/20260911204446.1719356-1-pc%40manguebit.org Fixes: df0e03a4fb94 ("smb: client: fix potential deadlock when reconnecting channels") Signed-off-by: Paulo Alcantara Cc: David Howells Cc: Shyam Prasad N Cc: Ronnie Sahlberg Cc: Tom Talpey Cc: Bharath SM Cc: Namjae Jeon Cc: stable@vger.kernel.org --- fs/smb/client/connect.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index bef710d9a3c3..4bd9f9fb93bb 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -174,6 +174,8 @@ cifs_signal_cifsd_for_reconnect(struct TCP_Server_Info *server, nserver = ses->chans[i].server; if (!nserver) continue; + if (!list_empty(&nserver->rlist)) + continue; nserver->srv_count++; list_add(&nserver->rlist, &reco); } @@ -182,11 +184,15 @@ cifs_signal_cifsd_for_reconnect(struct TCP_Server_Info *server, } } + spin_lock(&cifs_tcp_ses_lock); list_for_each_entry_safe(server, nserver, &reco, rlist) { list_del_init(&server->rlist); set_need_reco(server); + spin_unlock(&cifs_tcp_ses_lock); cifs_put_tcp_session(server, 0); + spin_lock(&cifs_tcp_ses_lock); } + spin_unlock(&cifs_tcp_ses_lock); } /* @@ -1824,6 +1830,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx, spin_lock_init(&tcp_ses->mid_counter_lock); INIT_LIST_HEAD(&tcp_ses->tcp_ses_list); INIT_LIST_HEAD(&tcp_ses->smb_ses_list); + INIT_LIST_HEAD(&tcp_ses->rlist); INIT_DELAYED_WORK(&tcp_ses->echo, cifs_echo_request); INIT_DELAYED_WORK(&tcp_ses->reconnect, smb2_reconnect_server); mutex_init(&tcp_ses->reconnect_mutex); -- 2.55.0