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sched: Fix __sched_setscheduler() nice test 

With the introduction of sched_attr::sched_nice we need to check
if we've got permission to actually change the nice value.

Daniel found that can_nice() would always fail; and upon
inspection it turns out that can_nice() only tests to see if we
can lower the nice value, but it doesn't validate if we're
lowering or not.

Therefore amend the test to only call can_nice() when we lower
the nice value.

Reported-and-Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: raistlin@linux.it
Cc: juri.lelli@gmail.com
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Fixes: d50dde5a10 ("sched: Add new scheduler syscalls to support an extended scheduling parameters ABI")
Link: http://lkml.kernel.org/r/20140116165425.GA9481@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-01-16 17:54:25 +01:00 committed by Ingo Molnar
parent 7479f3c9cf
commit eaad45132c
1 changed files with 2 additions and 1 deletions
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3
kernel/sched/core.c
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@ -3296,7 +3296,8 @@ static int __sched_setscheduler(struct task_struct *p,
*/
if (user && !capable(CAP_SYS_NICE)) {
if (fair_policy(policy)) {
if (!can_nice(p, attr->sched_nice))
if (attr->sched_nice < TASK_NICE(p) &&
!can_nice(p, attr->sched_nice))
return -EPERM;
}