Commit-ID: d8d28c8f00e84a72e8bee39a85835635417bee49
Gitweb: http://git.kernel.org/tip/d8d28c8f00e84a72e8bee39a85835635417bee49
Author: Daniel Bristot de Oliveira <[email protected]>
AuthorDate: Tue, 22 Jul 2014 23:27:41 -0300
Committer: Ingo Molnar <[email protected]>
CommitDate: Mon, 28 Jul 2014 10:00:08 +0200
sched: Fix sched_setparam() policy == -1 logic
The scheduler uses policy == -1 to preserve the current policy state to
implement sched_setparam(). But, as (int) -1 is equals to 0xffffffff,
it's matching the if (policy & SCHED_RESET_ON_FORK) on
_sched_setscheduler(). This match changes the policy value to an
invalid value, breaking the sched_setparam() syscall.
This patch checks policy == -1 before check the SCHED_RESET_ON_FORK flag.
The following program shows the bug:
int main(void)
{
struct sched_param param = {
.sched_priority = 5,
};
sched_setscheduler(0, SCHED_FIFO, ¶m);
param.sched_priority = 1;
sched_setparam(0, ¶m);
param.sched_priority = 0;
sched_getparam(0, ¶m);
if (param.sched_priority != 1)
printf("failed priority setting (found %d instead of 1)\n",
param.sched_priority);
else
printf("priority setting fine\n");
}
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Reviewed-by: Steven Rostedt <[email protected]>
Cc: <[email protected]> # 3.14+
Cc: Linus Torvalds <[email protected]>
Cc: [email protected]
Fixes: 7479f3c9cf67 "sched: Move SCHED_RESET_ON_FORK into attr::sched_flags"
Link:
http://lkml.kernel.org/r/9ebe0566a08dbbb3999759d3f20d6004bb2dbcfa.1406079891.git.bris...@redhat.com
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched/core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bc1638b..0acf96b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3558,9 +3558,10 @@ static int _sched_setscheduler(struct task_struct *p,
int policy,
};
/*
- * Fixup the legacy SCHED_RESET_ON_FORK hack
+ * Fixup the legacy SCHED_RESET_ON_FORK hack, except if
+ * the policy=-1 was passed by sched_setparam().
*/
- if (policy & SCHED_RESET_ON_FORK) {
+ if ((policy != -1) && (policy & SCHED_RESET_ON_FORK)) {
attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
policy &= ~SCHED_RESET_ON_FORK;
attr.sched_policy = policy;
--
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