linux-kernel - Re: [PATCH RFC 0/3] A few round_pipe

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Message-ID: <201487e9-235c-8604-50f2-02bd1170d8e8@infradead.org>
Date:   Thu, 14 Sep 2017 09:57:12 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     mtk.manpages@...il.com, Joe Lawrence <joe.lawrence@...hat.com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Mikulas Patocka <mpatocka@...hat.com>
Subject: Re: [PATCH RFC 0/3] A few round_pipe_size() and pipe-max-size fixups

On 09/14/17 06:26, Michael Kerrisk (man-pages) wrote:
> Hello Joe,
> 
> On 5 September 2017 at 16:44, Joe Lawrence <joe.lawrence@...hat.com> wrote:
>> While backporting Michael's "pipe: fix limit handling" [1] patchset to a
>> distro-kernel, Mikulas noticed that current upstream pipe limit handling
>> contains a few problems:
>>
>>   1 - round_pipe_size() nr_pages overflow on 32bit:  this would
>>       subsequently try roundup_pow_of_two(0), which is undefined.

Hi,
Sorry I missed the initial posting of this.

The man page for F_SETPIPE_SZ (http://man7.org/linux/man-pages/man2/fcntl.2.html)
says:
"Attempts to set the pipe capacity below the page size are
silently rounded up to the page size."

That implies to me that setting pipe size to 0 would round up to PAGE_SIZE.
Doesn't patch 1/3 change that to return -EINVAL?


Otherwise all 3 patches look good to me.

thanks,
-- 
~Randy