linux-kernel - [PATCH 2/3] hrtimer: Catch illegal clockids

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Date:	Fri, 15 Jan 2016 17:41:09 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	<linux-kernel@...r.kernel.org>, Tomasz Nowicki <tn@...ihalf.com>,
	Christoffer Dall <christoffer.dall@...aro.org>
Subject: [PATCH 2/3] 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@....com>
---
 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;
 }
 
 /*
-- 
2.1.4