This is a note to let you know that I've just added the patch titled
sched/deadline: Restrict user params max value to 2^63 ns
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-deadline-restrict-user-params-max-value-to-2-63-ns.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From b0827819b0da4acfbc1df1e05edcf50efd07cbd1 Mon Sep 17 00:00:00 2001
From: Juri Lelli <[email protected]>
Date: Tue, 13 May 2014 14:11:31 +0200
Subject: sched/deadline: Restrict user params max value to 2^63 ns
From: Juri Lelli <[email protected]>
commit b0827819b0da4acfbc1df1e05edcf50efd07cbd1 upstream.
Michael Kerrisk noticed that creating SCHED_DEADLINE reservations
with certain parameters (e.g, a runtime of something near 2^64 ns)
can cause a system freeze for some amount of time.
The problem is that in the interface we have
u64 sched_runtime;
while internally we need to have a signed runtime (to cope with
budget overruns)
s64 runtime;
At the time we setup a new dl_entity we copy the first value in
the second. The cast turns out with negative values when
sched_runtime is too big, and this causes the scheduler to go crazy
right from the start.
Moreover, considering how we deal with deadlines wraparound
(s64)(a - b) < 0
we also have to restrict acceptable values for sched_{deadline,period}.
This patch fixes the thing checking that user parameters are always
below 2^63 ns (still large enough for everyone).
It also rewrites other conditions that we check, since in
__checkparam_dl we don't have to deal with deadline wraparounds
and what we have now erroneously fails when the difference between
values is too big.
Reported-by: Michael Kerrisk <[email protected]>
Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Juri Lelli <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Dario Faggioli<[email protected]>
Cc: Dave Jones <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/sched/core.c | 37 ++++++++++++++++++++++++++++++-------
1 file changed, 30 insertions(+), 7 deletions(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3242,17 +3242,40 @@ __getparam_dl(struct task_struct *p, str
* We ask for the deadline not being zero, and greater or equal
* than the runtime, as well as the period of being zero or
* greater than deadline. Furthermore, we have to be sure that
- * user parameters are above the internal resolution (1us); we
- * check sched_runtime only since it is always the smaller one.
+ * user parameters are above the internal resolution of 1us (we
+ * check sched_runtime only since it is always the smaller one) and
+ * below 2^63 ns (we have to check both sched_deadline and
+ * sched_period, as the latter can be zero).
*/
static bool
__checkparam_dl(const struct sched_attr *attr)
{
- return attr && attr->sched_deadline != 0 &&
- (attr->sched_period == 0 ||
- (s64)(attr->sched_period - attr->sched_deadline) >= 0) &&
- (s64)(attr->sched_deadline - attr->sched_runtime ) >= 0 &&
- attr->sched_runtime >= (2 << (DL_SCALE - 1));
+ /* deadline != 0 */
+ if (attr->sched_deadline == 0)
+ return false;
+
+ /*
+ * Since we truncate DL_SCALE bits, make sure we're at least
+ * that big.
+ */
+ if (attr->sched_runtime < (1ULL << DL_SCALE))
+ return false;
+
+ /*
+ * Since we use the MSB for wrap-around and sign issues, make
+ * sure it's not set (mind that period can be equal to zero).
+ */
+ if (attr->sched_deadline & (1ULL << 63) ||
+ attr->sched_period & (1ULL << 63))
+ return false;
+
+ /* runtime <= deadline <= period (if period != 0) */
+ if ((attr->sched_period != 0 &&
+ attr->sched_period < attr->sched_deadline) ||
+ attr->sched_deadline < attr->sched_runtime)
+ return false;
+
+ return true;
}
/*
Patches currently in stable-queue which might be from [email protected] are
queue-3.14/sched-deadline-fix-memory-leak.patch
queue-3.14/sched-deadline-restrict-user-params-max-value-to-2-63-ns.patch
queue-3.14/sched-deadline-change-sched_getparam-behaviour-vs-sched_deadline.patch
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