Re: [PATCH] prevent timespec/timeval to ktime_t overflow

Thomas Gleixner
2006-09-01T08:52:31Z

On Thu, 2006-08-31 at 20:46 -0700, Andrew Morton wrote:
> > * 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 };
> > }
> >
>
> This makes my FC3 x86_64 testbox hang during udev startup. sysrq-T trace at
> http://www.zip.com.au/~akpm/linux/patches/stuff/log-x.

Does not help much.

> I had a quick look at the args to hrtimer_nanosleep and all seems to be in
> order.

Hmm. I can not reproduce that on any one of my boxen. Can you please try
with this debug variant, so we have a chance to figure out what's wrong.

tglx

Index: linux-2.6.18-rc5/include/linux/ktime.h
===================================================================
--- linux-2.6.18-rc5.orig/include/linux/ktime.h 2006-08-31 18:58:32.000000000 +0200
+++ linux-2.6.18-rc5/include/linux/ktime.h 2006-09-01 10:47:59.000000000 +0200
@@ -57,6 +57,7 @@ typedef union {
} ktime_t;

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

/*
* ktime_t definitions when using the 64-bit scalar representation:
@@ -73,6 +74,13 @@ 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)) {
+ printk("ktime_set: %ld : %lu\n", secs, nsecs);
+ WARN_ON(1);
+ return (ktime_t){ .tv64 = KTIME_MAX };
+ }
+#endif
return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
}