From ff1fa2081d173b01cebe2fbf0a2d0f1cee9ce4b5 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 29 Jun 2022 11:19:10 -0700 Subject: [PATCH] net: tun: avoid disabling NAPI twice Eric reports that syzbot made short work out of my speculative fix. Indeed when queue gets detached its tfile->tun remains, so we would try to stop NAPI twice with a detach(), close() sequence. Alternative fix would be to move tun_napi_disable() to tun_detach_all() and let the NAPI run after the queue has been detached. Fixes: a8fc8cb5692a ("net: tun: stop NAPI when detaching queues") Reported-by: syzbot Reported-by: Eric Dumazet Reviewed-by: Eric Dumazet Link: https://lore.kernel.org/r/20220629181911.372047-1-kuba@kernel.org Signed-off-by: Jakub Kicinski --- drivers/net/tun.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index e2eb35887394..259b2b84b2b3 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -640,7 +640,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean) tun = rtnl_dereference(tfile->tun); if (tun && clean) { - tun_napi_disable(tfile); + if (!tfile->detached) + tun_napi_disable(tfile); tun_napi_del(tfile); }