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    Subject[tip:sched/core] sched/core: Check quota and period overflow at usec to nsec conversion
    Commit-ID:  1a8b4540db732ca16c9e43ac7c08b1b8f0b252d8
    Gitweb: https://git.kernel.org/tip/1a8b4540db732ca16c9e43ac7c08b1b8f0b252d8
    Author: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
    AuthorDate: Wed, 27 Feb 2019 11:10:20 +0300
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Fri, 19 Apr 2019 13:42:10 +0200

    sched/core: Check quota and period overflow at usec to nsec conversion

    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@yandex-team.ru>
    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/155125502079.293431.3947497929372138600.stgit@buzz
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    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 685b1541ce51..de8ab411826c 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -6611,8 +6611,10 @@ static 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);
    }
    @@ -6634,6 +6636,9 @@ static 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;

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