On Wed, Apr 04, 2007 at 11:30:48PM +0200, Thomas Gleixner wrote:
> On Wed, 2007-04-04 at 23:11 +0200, Adrian Bunk wrote:
> > On Wed, Mar 14, 2007 at 11:00:12AM +0100, Thomas Gleixner wrote:
> > > hrtimer_forward() does not check for the possible overflow of
> > > timer->expires. This can happen on 64 bit machines with large interval
> > > values and results currently in an endless loop in the softirq because
> > > the expiry value becomes negative and therefor the timer is expired all
> > > the time.
> > >
> > > Check for this condition and set the expiry value to the max. expiry
> > > time in the future.
> > >
> > > The fix should be applied to stable kernel series as well.
> >
> >
> > Is this relevant for 2.6.16?
> >
> > I'm asking since KTIME_SEC_MAX is not used in 2.6.16, and therefore the
> > check in ktime_set() is also missing.
>
> KTIME_SEC_MAX was introduced with commit
> 96dd7421a06a5bc6eb731323b95efcb2fd864854
>
> to fix a conversion problem on 64 bit machines, which is also present in
> 2.6.16 AFAICT.
>
> The patch just makes use of this constant. So you need to pull it as
> well.
Thanks, below is what I applied.
> tglx
cu
Adrian
Thomas Gleixner (3):
prevent timespec/timeval to ktime_t overflow
fix MTIME_SEC_MAX on 32-bit
hrtimer: prevent overrun DoS in hrtimer_forward()
diff --git a/include/linux/ktime.h b/include/linux/ktime.h
index f3dec45..4548ddb 100644
--- a/include/linux/ktime.h
+++ b/include/linux/ktime.h
@@ -56,7 +56,12 @@ typedef union {
#endif
} ktime_t;
-#define KTIME_MAX (~((u64)1 << 63))
+#define KTIME_MAX ((s64)~((u64)1 << 63))
+#if (BITS_PER_LONG == 64)
+# define KTIME_SEC_MAX (KTIME_MAX / NSEC_PER_SEC)
+#else
+# define KTIME_SEC_MAX LONG_MAX
+#endif
/*
* ktime_t definitions when using the 64-bit scalar representation:
@@ -77,6 +82,10 @@ 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 };
}
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 14bc9cf..a29ceb0 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -316,6 +316,12 @@ hrtimer_forward(struct hrtimer *timer, ktime_t interval)
orun++;
}
timer->expires = ktime_add(timer->expires, interval);
+ /*
+ * Make sure, that the result did not wrap with a very large
+ * interval.
+ */
+ if (timer->expires.tv64 < 0)
+ timer->expires = ktime_set(KTIME_SEC_MAX, 0);
return orun;
}
-
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