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SubjectRe: sched: Disallow sched_attr::sched_policy < 0
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On Tue, Jun 3, 2014 at 10:08 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Mon, Jun 02, 2014 at 04:22:04PM -0400, Dave Jones wrote:
>> On Mon, Jun 02, 2014 at 02:13:19AM +0000, Linux Kernel wrote:
>>
>> > sched: Disallow sched_attr::sched_policy < 0
>> >
>> > The scheduler uses policy=-1 to preserve the current policy state to
>> > implement sys_sched_setparam(), this got exposed to userspace by
>> > accident through sys_sched_setattr(), cure this.
>> >
>> > ---
>> > kernel/sched/core.c | 3 +++
>> > 1 files changed, 3 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> > index f2205f0..cdefcf7 100644
>> > --- a/kernel/sched/core.c
>> > +++ b/kernel/sched/core.c
>> > @@ -3662,6 +3662,9 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
>> > if (retval)
>> > return retval;
>> >
>> > + if (attr.sched_policy < 0)
>> > + return -EINVAL;
>> > +
>> > rcu_read_lock();
>> > retval = -ESRCH;
>> > p = find_process_by_pid(pid);
>>
>> Todays coverity run picked up..
>>
>> 3687
>> >>> CID 1219934: Unsigned compared against 0 (NO_EFFECT)
>> >>> This less-than-zero comparison of an unsigned value is never true. "attr.sched_policy < 0U".
>> 3688 if (attr.sched_policy < 0)
>> 3689 return -EINVAL;
>>
>
> Once upon a time GCC also did warns like that, but my compiler is silent
> :-(
>
> Yes, that needs fixing..

I sent already a patch for that...

--
Thanks,
//richard


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