[lkml]   [2017]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: shmctl(SHM_STAT) vs. /proc/sysvipc/shm permissions discrepancies
Hello Michal,

On 20 December 2017 at 10:20, Michal Hocko <> wrote:
> On Tue 19-12-17 17:45:40, Michael Kerrisk wrote:
>> But, is
>> there a pressing reason to make the change? (Okay, I guess iterating
>> using *_STAT is nicer than parsing /proc/sysvipc/*.)
> The reporter of this issue claims that "Reading /proc/sysvipc/shm is way
> slower than executing the system call." I haven't checked that but I can
> imagine that /proc/sysvipc/shm can take quite some time when there are
> _many_ segments registered.

Yes, that makes sense.

> So they would like to use the syscall but
> the interacting parties do not have compatible permissions.

So, I don't think there is any security issue, since the same info is
available in /proc/sysvipc/*. The only question would be whether
change in the *_STAT behavior might surprise some applications into
behaving differently. I presume the chances of that are low, but if it
was a concert, one could add new shmctl/msgctl/semctl *_STAT_ALL (or
some such) operations that have the desired behavior.



Michael Kerrisk
Linux man-pages maintainer;
Linux/UNIX System Programming Training:

 \ /
  Last update: 2017-12-20 17:19    [W:0.059 / U:0.500 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site