linux-kernel - [PATCH 2/2] 9p: trans_fd/p9_conn_cancel: drop client lock earlier

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Message-Id: <20220904064028.1305220-1-asmadeus@codewreck.org>
Date:   Sun,  4 Sep 2022 15:40:28 +0900
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     v9fs-developer@...ts.sourceforge.net
Cc:     syzkaller-bugs@...glegroups.com, linux_oss@...debyte.com,
        linux-kernel@...r.kernel.org,
        Dominique Martinet <asmadeus@...ewreck.org>,
        syzbot+50f7e8d06c3768dd97f3@...kaller.appspotmail.com,
        Schspa Shi <schspa@...il.com>
Subject: [PATCH 2/2] 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.

Reported-by: syzbot+50f7e8d06c3768dd97f3@...kaller.appspotmail.com
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
Tested-by: Schspa Shi <schspa@...il.com>
---
 net/9p/trans_fd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index e758978b44be..60fcc6b30b46 100644
--- 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
-- 
2.35.1