netdev - Re: [PATCH v2 5/8] net: af_can: do not leave a dangling sk pointer in can

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Message-ID: <CAMZ6RqJ8XBVd5RzKEtxKz8hp9sR7g6fzwLv_3aB1OUSuK_dBFA@mail.gmail.com>
Date: Tue, 8 Oct 2024 11:37:48 +0900
From: Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To: Ignat Korchagin <ignat@...udflare.com>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Marcel Holtmann <marcel@...tmann.org>, 
	Johan Hedberg <johan.hedberg@...il.com>, Luiz Augusto von Dentz <luiz.dentz@...il.com>, 
	Oliver Hartkopp <socketcan@...tkopp.net>, Marc Kleine-Budde <mkl@...gutronix.de>, 
	Alexander Aring <alex.aring@...il.com>, Stefan Schmidt <stefan@...enfreihafen.org>, 
	Miquel Raynal <miquel.raynal@...tlin.com>, David Ahern <dsahern@...nel.org>, 
	Willem de Bruijn <willemdebruijn.kernel@...il.com>, linux-bluetooth@...r.kernel.org, 
	linux-can@...r.kernel.org, linux-wpan@...r.kernel.org, 
	kernel-team@...udflare.com, kuniyu@...zon.com, alibuda@...ux.alibaba.com
Subject: Re: [PATCH v2 5/8] net: af_can: do not leave a dangling sk pointer in can_create()

Hi Ignat,

Thanks for the patch.

On Tue. 8 Oct. 2024 at 06:37, Ignat Korchagin <ignat@...udflare.com> wrote:
> On error can_create() frees the allocated sk object, but sock_init_data()
> has already attached it to the provided sock object. This will leave a
> dangling sk pointer in the sock object and may cause use-after-free later.

I was about to suggest that this should be backported to stable, but
after reading the cover letter, I now understand that this patch is
more an improvement to avoid false positives on kmemleak & Cie. Maybe
the description could be a bit more nuanced? After patch 1/8 of this
series, it seems that the use-after-free is not possible anymore.

> Signed-off-by: Ignat Korchagin <ignat@...udflare.com>

See above comment as notwithstanding. This said:

Reviewed-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>


> ---
>  net/can/af_can.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/net/can/af_can.c b/net/can/af_can.c
> index 707576eeeb58..01f3fbb3b67d 100644
> --- a/net/can/af_can.c
> +++ b/net/can/af_can.c
> @@ -171,6 +171,7 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
>                 /* release sk on errors */
>                 sock_orphan(sk);
>                 sock_put(sk);
> +               sock->sk = NULL;
>         }
>
>   errout:
> --
> 2.39.5
>
>