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From: Christian Brauner <christian.brauner@ubuntu.com>
To: Christoph Hellwig <hch@lst.de>
Cc: davem@davemloft.net, kuba@kernel.org, ast@kernel.org,
	daniel@iogearbox.net, netdev@vger.kernel.org,
	bpf@vger.kernel.org, Rodrigo Madera <rodrigo.madera@gmail.com>
Subject: Re: [PATCH net] net/bpfilter: initialize pos in __bpfilter_process_sockopt
Date: Thu, 30 Jul 2020 18:13:03 +0200
Message-ID: <20200730161303.erzgrhqsgc77d4ny@wittgenstein> (raw)
In-Reply-To: <20200730160900.187157-1-hch@lst.de>

On Thu, Jul 30, 2020 at 06:09:00PM +0200, Christoph Hellwig wrote:
> __bpfilter_process_sockopt never initialized the pos variable passed to
> the pipe write.  This has been mostly harmless in the past as pipes
> ignore the offset, but the switch to kernel_write no verified the

s/no/now/

> position, which can lead to a failure depending on the exact stack
> initialization patter.  Initialize the variable to zero to make

s/patter/pattern/

> rw_verify_area happy.
> 
> Fixes: 6955a76fbcd5 ("bpfilter: switch to kernel_write")
> Reported-by: Christian Brauner <christian.brauner@ubuntu.com>
> Reported-by: Rodrigo Madera <rodrigo.madera@gmail.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Tested-by: Rodrigo Madera <rodrigo.madera@gmail.com>
> ---

Thanks for tracking this down, Christoph! This fixes the logging issue
for me.
Tested-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>

>  net/bpfilter/bpfilter_kern.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
> index 1905e01c3aa9a7..4494ea6056cdb8 100644
> --- a/net/bpfilter/bpfilter_kern.c
> +++ b/net/bpfilter/bpfilter_kern.c
> @@ -39,7 +39,7 @@ static int __bpfilter_process_sockopt(struct sock *sk, int optname,
>  {
>  	struct mbox_request req;
>  	struct mbox_reply reply;
> -	loff_t pos;
> +	loff_t pos = 0;
>  	ssize_t n;
>  	int ret = -EFAULT;
>  
> -- 
> 2.27.0
> 

  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 16:09 Christoph Hellwig
2020-07-30 16:13 ` Christian Brauner [this message]
2020-07-31  0:07   ` Daniel Borkmann
2020-08-01 19:48     ` Alexei Starovoitov
2020-08-03 14:56       ` Daniel Borkmann
2020-08-03 15:36         ` Rodrigo Madera

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