Re: [PATCH net v3 2/3] tun: fix inverted error check when re-attaching the filter

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Rongguang Wei wrote:
> From: Rongguang Wei <weirongguang@kylinos.cn>
> 
> tun_attach() returns early when sk_attach_filter_kern() succeeds instead of
> when it fails, so a queue attached to a persistent TAP is never published
> in tun->tfiles[] while TUNSETIFF still reported success.
> 
> Fix the check, so that a failed re-attach aborts the attach, and detach the
> filter again if a later step of tun_attach() fails.
> 
> This has to come after the patch that keeps a kernel copy of the program:
> with the check fixed but the program still read from the caller's address
> space, a re-attach that used to succeed without installing any filter would
> fail with -EFAULT or -EINVAL.
> 
> Fixes: 54f968d6efdb ("tuntap: move socket to tun_file")
> Link: https://lore.kernel.org/netdev/179027275318.2160803.4185895144088175048@kernel.org/
> Signed-off-by: Rongguang Wei <weirongguang@kylinos.cn>

Reviewed-by: Willem de Bruijn <willemb@google.com>