linux-kernel - Re: [PATCH net-next v3 2/3] tun: tun_chr_open(): correctly initialize socket uid

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Message-ID: <CANn89iLqDA_O3kFNdcJXcPQK+2jWXcN2CexVJYuexPGiuriq0g@mail.gmail.com>
Date:   Mon, 6 Feb 2023 09:29:51 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Pietro Borrello <borrello@...g.uniroma1.it>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Lorenzo Colitti <lorenzo@...gle.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jkl820.git@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 2/3] tun: tun_chr_open(): correctly initialize
 socket uid

On Sat, Feb 4, 2023 at 6:39 PM Pietro Borrello
<borrello@...g.uniroma1.it> wrote:
>
> sock_init_data() assumes that the `struct socket` passed in input is
> contained in a `struct socket_alloc` allocated with sock_alloc().
> However, tun_chr_open() passes a `struct socket` embedded in a `struct
> tun_file` allocated with sk_alloc().
> This causes a type confusion when issuing a container_of() with
> SOCK_INODE() in sock_init_data() which results in assigning a wrong
> sk_uid to the `struct sock` in input.
> On default configuration, the type confused field overlaps with the
> high 4 bytes of `struct tun_struct __rcu *tun` of `struct tun_file`,
> NULL at the time of call, which makes the uid of all tun sockets 0,
> i.e., the root one.
> Fix the assignment by using sock_init_data_uid().
>
> Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")
> Signed-off-by: Pietro Borrello <borrello@...g.uniroma1.it>
> ---

Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Thanks.