linux-kernel - Re: [PATCH] net/x25: Fix null-ptr-deref in x25

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Message-Id: <20200928.184326.1754311969939569006.davem@davemloft.net>
Date:   Mon, 28 Sep 2020 18:43:26 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     ms@....tdt.de
Cc:     andrew.hendry@...il.com, kuba@...nel.org, edumazet@...gle.com,
        xiyuyang19@...an.edu.cn, linux-x25@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/x25: Fix null-ptr-deref in x25_connect

From: Martin Schiller <ms@....tdt.de>
Date: Mon, 28 Sep 2020 11:23:27 +0200

> diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
> index 0bbb283f23c9..0524a5530b91 100644
> --- a/net/x25/af_x25.c
> +++ b/net/x25/af_x25.c
> @@ -820,7 +820,7 @@ static int x25_connect(struct socket *sock, struct sockaddr *uaddr,
>  
>  	rc = x25_wait_for_connection_establishment(sk);
>  	if (rc)
> -		goto out_put_neigh;
> +		goto out;

If x25_wait_for_connection_establishment() returns because of an interrupting
signal, we are not going to call x25_disconnect().

The case you are fixing only applies _sometimes_ when
x25_wait_for_connection_establishment() returns.  But not always.

That neighbour has to be released at this spot otherwise.