Re: [PATCH] Bluetooth: L2CAP: handle NULL sock pointer in l2cap_sock_alloc

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Fedor Pchelkin <pchelkin@ispras.ru>
Date: Wed, 18 Dec 2024 00:19:59 +0300
> A NULL sock pointer is passed into l2cap_sock_alloc() when it is called
> from l2cap_sock_new_connection_cb() and the error handling paths should
> also be aware of it.
> 
> Seemingly a more elegant solution would be to swap bt_sock_alloc() and
> l2cap_chan_create() calls since they are not interdependent to that moment
> but then l2cap_chan_create() adds the soon to be deallocated and still
> dummy-initialized channel to the global list accessible by many L2CAP
> paths. The channel would be removed from the list in short period of time
> but be a bit more straight-forward here and just check for NULL instead of
> changing the order of function calls.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE static
> analysis tool.
> 
> Fixes: 7c4f78cdb8e7 ("Bluetooth: L2CAP: do not leave dangling sk pointer on error in l2cap_sock_create()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>

Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>


> ---
>  net/bluetooth/l2cap_sock.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
> index 3d2553dcdb1b..49f97d4138ea 100644
> --- a/net/bluetooth/l2cap_sock.c
> +++ b/net/bluetooth/l2cap_sock.c
> @@ -1888,7 +1888,8 @@ static struct sock *l2cap_sock_alloc(struct net *net, struct socket *sock,
>  	chan = l2cap_chan_create();
>  	if (!chan) {
>  		sk_free(sk);
> -		sock->sk = NULL;
> +		if (sock)
> +			sock->sk = NULL;
>  		return NULL;
>  	}
>  
> -- 
> 2.39.5