Commit 96dd7421 authored Sep 06, 2006 by Thomas Gleixner Committed by Linus Torvalds Sep 06, 2006

[PATCH] prevent timespec/timeval to ktime_t overflow



Frank v.  Waveren pointed out that on 64bit machines the timespec to
ktime_t conversion might overflow.  This is also true for timeval to
ktime_t conversions.  This breaks a "sleep inf" on 64bit machines.

While a timespec/timeval with tx.sec = MAX_LONG is valid by specification
the internal representation of ktime_t is based on nanoseconds.  The
conversion of seconds to nanoseconds overflows for seconds values >=
(MAX_LONG / NSEC_PER_SEC).

Check the seconds argument to the conversion and limit it to the maximum
time which can be represented by ktime_t.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Frank v Waveren <fvw@var.cx>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent fe2bbc48

include/linux/ktime.h

+6 −1

Original line number	Diff line number	Diff line
		@@ -56,7 +56,8 @@ typedef union {
		#endif
		} ktime_t;

		#define KTIME_MAX (~((u64)1 << 63))
		#define KTIME_MAX ((s64)~((u64)1 << 63))
		#define KTIME_SEC_MAX (KTIME_MAX / NSEC_PER_SEC)

		/*
		* ktime_t definitions when using the 64-bit scalar representation:
		@@ -73,6 +74,10 @@ typedef union {
		*/
		static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
		{
		#if (BITS_PER_LONG == 64)
		if (unlikely(secs >= KTIME_SEC_MAX))
		return (ktime_t){ .tv64 = KTIME_MAX };
		#endif
		return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
		}