69 lines
2.1 KiB
Diff
69 lines
2.1 KiB
Diff
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Bugzilla: 1117942
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Upstream-status: Sent for 3.16 and seen by peterz
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The scheduler uses policy=-1 to preserve the current policy state to
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implement sched_setparam(). But, as (int) -1 is equals to 0xffffffff,
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it's matching the if (policy & SCHED_RESET_ON_FORK) on
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_sched_setscheduler(). This match changes the policy value to an
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invalid value, breaking the sched_setparam() syscall.
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This patch checks policy=-1 before check the SCHED_RESET_ON_FORK flag.
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The following program shows the bug:
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int main(void)
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{
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struct sched_param param = {
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.sched_priority = 5,
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};
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sched_setscheduler(0, SCHED_FIFO, ¶m);
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param.sched_priority = 1;
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sched_setparam(0, ¶m);
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param.sched_priority = 0;
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sched_getparam(0, ¶m);
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if (param.sched_priority != 1)
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printf("failed priority setting (found %d instead of 1)\n",
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param.sched_priority);
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else
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printf("priority setting fine\n");
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}
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Ingo Molnar <mingo@kernel.org>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Cc: stable@vger.kernel.org # 3.14+
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Fixes: 7479f3c9cf67 "sched: Move SCHED_RESET_ON_FORK into attr::sched_flags"
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Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
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Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
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---
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kernel/sched/core.c | 5 +++--
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1 file changed, 3 insertions(+), 2 deletions(-)
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diff --git a/kernel/sched/core.c b/kernel/sched/core.c
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index bc1638b..0acf96b 100644
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -3558,9 +3558,10 @@ static int _sched_setscheduler(struct task_struct *p, int policy,
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};
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/*
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- * Fixup the legacy SCHED_RESET_ON_FORK hack
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+ * Fixup the legacy SCHED_RESET_ON_FORK hack, except if
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+ * the policy=-1 was passed by sched_setparam().
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*/
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- if (policy & SCHED_RESET_ON_FORK) {
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+ if ((policy != -1) && (policy & SCHED_RESET_ON_FORK)) {
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attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
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policy &= ~SCHED_RESET_ON_FORK;
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attr.sched_policy = policy;
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--
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1.9.3
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--
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