[tip:timers/core] hrtimer: Catch illegal clockids

[tip-bot for Marc Zyngier <tipbot@zytor.com>]

Commit-ID:  9006a01829a50cfd6bbd4980910ed46e895e93d7
Gitweb:     http://git.kernel.org/tip/9006a01829a50cfd6bbd4980910ed46e895e93d7
Author:     Marc Zyngier <marc.zyngier@arm.com>
AuthorDate: Fri, 15 Jan 2016 17:41:09 +0000
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 27 Jan 2016 12:38:04 +0100

hrtimer: Catch illegal clockids

It is way too easy to take any random clockid and feed it to
the hrtimer subsystem. At best, it gets mapped to a monotonic
base, but it would be better to just catch illegal values as
early as possible.

This patch does exactly that, mapping illegal clockids to an
illegal base index, and panicing when we detect the illegal
condition.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Tomasz Nowicki <tn@semihalf.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Link: http://lkml.kernel.org/r/1452879670-16133-3-git-send-email-marc.zyngier@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/time/hrtimer.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index a125f22..cb0fe70 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -99,6 +99,9 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
 };
 
 static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
+	/* Make sure we catch unsupported clockids */
+	[0 ... MAX_CLOCKS - 1]	= HRTIMER_MAX_CLOCK_BASES,
+
 	[CLOCK_REALTIME]	= HRTIMER_BASE_REALTIME,
 	[CLOCK_MONOTONIC]	= HRTIMER_BASE_MONOTONIC,
 	[CLOCK_MONOTONIC_RAW]	= HRTIMER_BASE_MONOTONIC_RAW,
@@ -108,7 +111,9 @@ static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
 
 static inline int hrtimer_clockid_to_base(clockid_t clock_id)
 {
-	return hrtimer_clock_to_base_table[clock_id];
+	int base = hrtimer_clock_to_base_table[clock_id];
+	BUG_ON(base == HRTIMER_MAX_CLOCK_BASES);
+	return base;
 }
 
 /*