[PATCH 3/3] sched/core: check quota and period overflow at usec to nsec conversion

[Konstantin Khlebnikov]

Large values could overflow u64 and pass following sanity checks.

# echo 18446744073750000 > cpu.cfs_period_us
# cat cpu.cfs_period_us
40448

# echo 18446744073750000 > cpu.cfs_quota_us
# cat cpu.cfs_quota_us
40448

After this patch they will fail with -EINVAL.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
 kernel/sched/core.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a626fbd9fdc7..5f46aa335b28 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6606,8 +6606,10 @@ int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
 	period = ktime_to_ns(tg->cfs_bandwidth.period);
 	if (cfs_quota_us < 0)
 		quota = RUNTIME_INF;
-	else
+	else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
 		quota = (u64)cfs_quota_us * NSEC_PER_USEC;
+	else
+		return -EINVAL;
 
 	return tg_set_cfs_bandwidth(tg, period, quota);
 }
@@ -6629,6 +6631,9 @@ int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
 {
 	u64 quota, period;
 
+	if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC)
+		return -EINVAL;
+
 	period = (u64)cfs_period_us * NSEC_PER_USEC;
 	quota = tg->cfs_bandwidth.quota;