Bug#381905: linux-kernel-headers: NGROUPS_MAX doesn't match the kernel and causes test failures

[Jeff Bailey <jbailey@raspberryginger.com>]

On Mon, Aug 07, 2006 at 11:43:07AM -0600, Vladislav Yasevich wrote:

> We have tracked this down to a mismatch in the definitions of NGROUPS_MAX
> between the 2.6.8 Debian kernel and the linux-kernel-headers package.
> The linux-kernel-headers package defines this value as 32, while the
> kernel defines it as 65535.   When the test tries to retrieve this
> maximum value using the sysconf() call, it gets the value of 32 that
> was retrieved from glibc and specified by /usr/include/linux/limits.h,
> which is part of the linux-kernel-headers package.   The test then tries
> to issue a setgroups() call with the number of groups set to NGROUPS_MAX+1 (33)
> which is less then the kernel maximum (65535), and thus the call succeeds
> when it should really fail.

This is a place where the LTP fails regularily.  The correct solution is
to read the value from /proc/sys/kernel/ngroups_max.  I'd be happy to
talk about it on #ltp on freenode - I fixed this for pid_max in ltp in a
few places over the end of last week and the weekend.

The kernel headers do not necessarily match the running kernel.  Please
don't count on it.

Tks,
Jeff Bailey

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