linux-kernel - Re: [PATCH 4/8] pipe: fix limit checking in pipe_set

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Date:   Sun, 21 Aug 2016 12:33:44 +0200
From:   Vegard Nossum <vegard.nossum@...cle.com>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Willy Tarreau <w@....eu>, socketpair@...il.com,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Jens Axboe <axboe@...com>, Al Viro <viro@...iv.linux.org.uk>,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/8] pipe: fix limit checking in pipe_set_size()

On 08/20/2016 01:17 AM, Michael Kerrisk (man-pages) wrote:
> On 08/20/2016 08:56 AM, Michael Kerrisk (man-pages) wrote:
>> On 08/19/2016 08:30 PM, Vegard Nossum wrote:
>>> Is there any reason why we couldn't do the (size > pipe_max_size) check
>>> before calling account_pipe_buffers()?
>>
>> No reason that I can see. Just a little more work to be done in the
>> code, I think.
>
> And, just so I make sure we're understanding each other... I assume you
> mean changing the code here to something like:
[...]
>         if (nr_pages > pipe->buffers &&
>                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
>                 return -EPERM;
>
>         user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
>
>         if (nr_pages > pipe->buffers &&
>                         too_many_pipe_buffers_hard(user_bufs ||
>                         too_many_pipe_buffers_soft(user_bufs)) &&
>                         !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
>                 ret = -EPERM;
>                 goto out_revert_acct;
>         }
>
> Right?

Yup, that's what I had in mind. (The parantheses are messed up though.)


Vegard