9p: trans_fd/p9_conn_cancel: drop client lock earlier

syzbot reported a double-lock here and we no longer need this
lock after requests have been moved off to local list:
just drop the lock earlier.

Link: https://lkml.kernel.org/r/20220904064028.1305220-1-asmadeus@codewreck.org
Reported-by: syzbot+50f7e8d06c3768dd97f3@syzkaller.appspotmail.com
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Tested-by: Schspa Shi <schspa@gmail.com>

diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index e758978..60fcc6b 100644 (file)
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -205,6 +205,8 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
                list_move(&req->req_list, &cancel_list);
        }
 
+       spin_unlock(&m->client->lock);
+
        list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) {
                p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req);
                list_del(&req->req_list);
@@ -212,7 +214,6 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
                        req->t_err = err;
                p9_client_cb(m->client, req, REQ_STATUS_ERROR);
        }
-       spin_unlock(&m->client->lock);
 }
 
 static __poll_t