netdev - Re: [PATCH net] net/bpfilter: initialize pos in __bpfilter_process

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Date:   Fri, 31 Jul 2020 02:07:42 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Christian Brauner <christian.brauner@...ntu.com>,
        Christoph Hellwig <hch@....de>
Cc:     davem@...emloft.net, kuba@...nel.org, ast@...nel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Rodrigo Madera <rodrigo.madera@...il.com>
Subject: Re: [PATCH net] net/bpfilter: initialize pos in
 __bpfilter_process_sockopt

On 7/30/20 6:13 PM, Christian Brauner wrote:
> 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@...ntu.com>
>> Reported-by: Rodrigo Madera <rodrigo.madera@...il.com>
>> Signed-off-by: Christoph Hellwig <hch@....de>
>> Tested-by: Rodrigo Madera <rodrigo.madera@...il.com>
>> ---
> 
> Thanks for tracking this down, Christoph! This fixes the logging issue
> for me.
> Tested-by: Christian Brauner <christian.brauner@...ntu.com>
> Reviewed-by: Christian Brauner <christian.brauner@...ntu.com>

Applied to bpf & fixed up the typos in the commit msg, thanks everyone!