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net: tun: avoid disabling NAPI twice

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commit ff1fa2081d upstream.

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: a8fc8cb569 ("net: tun: stop NAPI when detaching queues")
Reported-by: syzbot <syzkaller@googlegroups.com>
Reported-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20220629181911.372047-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jakub Kicinski 2022-06-29 11:19:10 -07:00 committed by Greg Kroah-Hartman
parent 59c51c3b54
commit c36d41b65e
1 changed files with 2 additions and 1 deletions
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3
drivers/net/tun.c
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@ -646,7 +646,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
tun = rtnl_dereference(tfile->tun); tun = rtnl_dereference(tfile->tun);
if (tun && clean) { if (tun && clean) {
tun_napi_disable(tfile); if (!tfile->detached)
tun_napi_disable(tfile);
tun_napi_del(tfile); tun_napi_del(tfile);
} }