lkml.org 
[lkml]   [2017]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH RFC 0/3] A few round_pipe_size() and pipe-max-size fixups
From
Date
On 09/14/2017 12:57 PM, Randy Dunlap wrote:
> On 09/14/17 06:26, Michael Kerrisk (man-pages) wrote:
>> Hello Joe,
>>
>> On 5 September 2017 at 16:44, Joe Lawrence <joe.lawrence@redhat.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?

Good catch. How about something like this:

/*
* Minimum pipe size, as required by POSIX
*/
unsigned int pipe_min_size = PAGE_SIZE;

...

static inline unsigned int round_pipe_size(unsigned int size)
{
unsigned long nr_pages;

+ if (size < pipe_min_size)
+ size = pipe_min_size;
+
nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (nr_pages == 0)
return 0;

>
> Otherwise all 3 patches look good to me.

If the above is good, I can fold this into patch 1 and respin the set.

Thanks,

-- Joe

\
 
 \ /
  Last update: 2017-09-14 21:19    [W:0.190 / U:0.704 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site