linux-kernel - Re: [PATCH] Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_ready

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Message-ID: <ZHH+l73YeZd9iq52@corigine.com>
Date:   Sat, 27 May 2023 14:59:04 +0200
From:   Simon Horman <simon.horman@...igine.com>
To:     Sungwoo Kim <iam@...g-woo.kim>
Cc:     benquike@...il.com, davem@...emloft.net, daveti@...due.edu,
        edumazet@...gle.com, happiness.sung.woo@...il.com,
        johan.hedberg@...il.com, kuba@...nel.org,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
        luiz.dentz@...il.com, marcel@...tmann.org, netdev@...r.kernel.org,
        pabeni@...hat.com, wuruoyu@...com
Subject: Re: [PATCH] Bluetooth: L2CAP: Fix use-after-free in
 l2cap_sock_ready_cb

On Fri, May 26, 2023 at 02:16:48PM -0400, Sungwoo Kim wrote:
> >    net/bluetooth/l2cap_sock.c: In function 'l2cap_sock_release':
> > >> net/bluetooth/l2cap_sock.c:1418:9: error: implicit declaration of function 'l2cap_sock_cleanup_listen'; did you mean 'l2cap_sock_listen'? [-Werror=implicit-function-declaration]
> 
> Fix this error
> 
> >     1418 |         l2cap_sock_cleanup_listen(sk);
> >          |         ^~~~~~~~~~~~~~~~~~~~~~~~~
> >          |         l2cap_sock_listen
> >    net/bluetooth/l2cap_sock.c: At top level:
> > >> net/bluetooth/l2cap_sock.c:1436:13: warning: conflicting types for 'l2cap_sock_cleanup_listen'; have 'void(struct sock *)'
> >     1436 | static void l2cap_sock_cleanup_listen(struct sock *parent)
> >          |             ^~~~~~~~~~~~~~~~~~~~~~~~~
> > >> net/bluetooth/l2cap_sock.c:1436:13: error: static declaration of 'l2cap_sock_cleanup_listen' follows non-static declaration
> >    net/bluetooth/l2cap_sock.c:1418:9: note: previous implicit declaration of 'l2cap_sock_cleanup_listen' with type 'void(struct sock *)'
> >     1418 |         l2cap_sock_cleanup_listen(sk);
> >          |         ^~~~~~~~~~~~~~~~~~~~~~~~~
> >    cc1: some warnings being treated as errors
> 
> Signed-off-by: Sungwoo Kim <iam@...g-woo.kim>

Hi,

I am confused about why this error occurs.
In bluetooth-next [1] I see that l2cap_sock_cleanup_listen() is defined
on line  1435 of l2cap_sock.c. And then used on line 1574.
So there should be no need for a forward declaration.

[1] a088d769ef3a ("Bluetooth: L2CAP: Fix use-after-free")

> ---
>  net/bluetooth/l2cap_sock.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
> index eebe25610..3818e11a8 100644
> --- a/net/bluetooth/l2cap_sock.c
> +++ b/net/bluetooth/l2cap_sock.c
> @@ -46,6 +46,7 @@ static const struct proto_ops l2cap_sock_ops;
>  static void l2cap_sock_init(struct sock *sk, struct sock *parent);
>  static struct sock *l2cap_sock_alloc(struct net *net, struct socket *sock,
>  				     int proto, gfp_t prio, int kern);
> +static void l2cap_sock_cleanup_listen(struct sock *parent);
>  
>  bool l2cap_is_socket(struct socket *sock)
>  {
> @@ -1414,7 +1415,8 @@ static int l2cap_sock_release(struct socket *sock)
>  
>  	if (!sk)
>  		return 0;
> -
> +		

nit: The white-space on the line above was correct (no white-space)
     Now there are trailing tabs.

> +	l2cap_sock_cleanup_listen(sk);

This change may match the patch subject
but seems unrelated to the patch description.

>  	bt_sock_unlink(&l2cap_sk_list, sk);
>  
>  	err = l2cap_sock_shutdown(sock, SHUT_RDWR);
> -- 
> 2.34.1
> 
>