linux-kernel - [PATCH AUTOSEL 4.9 6/8] 9p: trans_fd/p9_conn

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Message-Id: <20221018001202.2732458-6-sashal@kernel.org>
Date:   Mon, 17 Oct 2022 20:12:00 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dominique Martinet <asmadeus@...ewreck.org>,
        syzbot+50f7e8d06c3768dd97f3@...kaller.appspotmail.com,
        Schspa Shi <schspa@...il.com>, Sasha Levin <sashal@...nel.org>,
        ericvh@...il.com, lucho@...kov.net, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        v9fs-developer@...ts.sourceforge.net, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 6/8] 9p: trans_fd/p9_conn_cancel: drop client lock earlier

From: Dominique Martinet <asmadeus@...ewreck.org>

[ Upstream commit 52f1c45dde9136f964d63a77d19826c8a74e2c7f ]

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@...kaller.appspotmail.com
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
Tested-by: Schspa Shi <schspa@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 33b317a25a2d..83cdb13c6322 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -215,6 +215,8 @@ 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);
@@ -222,7 +224,6 @@ 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 int
-- 
2.35.1