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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+b75c138e9286ac742647@syzkaller.appspotmail.com,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 4.19 10/33] net: tun: unlink NAPI from device on destruction
Date:   Tue,  5 Jul 2022 13:58:02 +0200
Message-Id: <20220705115607.012470204@linuxfoundation.org>
In-Reply-To: <20220705115606.709817198@linuxfoundation.org>
References: <20220705115606.709817198@linuxfoundation.org>
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From: Jakub Kicinski <kuba@kernel.org>

commit 3b9bc84d311104906d2b4995a9a02d7b7ddab2db upstream.

Syzbot found a race between tun file and device destruction.
NAPIs live in struct tun_file which can get destroyed before
the netdev so we have to del them explicitly. The current
code is missing deleting the NAPI if the queue was detached
first.

Fixes: 943170998b20 ("tun: enable NAPI for TUN/TAP driver")
Reported-by: syzbot+b75c138e9286ac742647@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20220623042039.2274708-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/tun.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -797,6 +797,7 @@ static void tun_detach_all(struct net_de
 		sock_put(&tfile->sk);
 	}
 	list_for_each_entry_safe(tfile, tmp, &tun->disabled, next) {
+		tun_napi_del(tfile);
 		tun_enable_queue(tfile);
 		tun_queue_purge(tfile);
 		xdp_rxq_info_unreg(&tfile->xdp_rxq);