From: Qais Yousef qais.yousef@arm.com
commit b562d140649966d4daedd0483a8fe59ad3bb465a upstream.
The check to ensure that the new written value into cpu.uclamp.{min,max} is within range, [0:100], wasn't working because of the signed comparison
7301 if (req.percent > UCLAMP_PERCENT_SCALE) { 7302 req.ret = -ERANGE; 7303 return req; 7304 }
# echo -1 > cpu.uclamp.min # cat cpu.uclamp.min 42949671.96
Cast req.percent into u64 to force the comparison to be unsigned and work as intended in capacity_from_percent().
# echo -1 > cpu.uclamp.min sh: write error: Numerical result out of range
Fixes: 2480c093130f ("sched/uclamp: Extend CPU's cgroup controller") Signed-off-by: Qais Yousef qais.yousef@arm.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lkml.kernel.org/r/20200114210947.14083-1-qais.yousef@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7260,7 +7260,7 @@ capacity_from_percent(char *buf) &req.percent); if (req.ret) return req; - if (req.percent > UCLAMP_PERCENT_SCALE) { + if ((u64)req.percent > UCLAMP_PERCENT_SCALE) { req.ret = -ERANGE; return req; }