[PATCH] sys_alarm() unsigned signed conversion fixup

alarm() calls the kernel with an unsigend int timeout in seconds.  The
value is stored in the tv_sec field of a struct timeval to setup the
itimer.  The tv_sec field of struct timeval is of type long, which causes
the tv_sec value to be negative on 32 bit machines if seconds > INT_MAX.

Before the hrtimer merge (pre 2.6.16) such a negative value was converted
to the maximum jiffies timeout by the timeval_to_jiffies conversion.  It's
not clear whether this was intended or just happened to be done by the
timeval_to_jiffies code.

hrtimers expect a timeval in canonical form and treat a negative timeout as
already expired.  This breaks the legitimate usage of alarm() with a
timeout value > INT_MAX seconds.

For 32 bit machines it is therefor necessary to limit the internal seconds
value to avoid API breakage.  Instead of doing this in all implementations
of sys_alarm the duplicated sys_alarm code is moved into a common function
in itimer.c

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 21 deletions

diff --git a/arch/mips/kernel/sysirix.c b/arch/mips/kernel/sysirix.c
index 0fc3730..5407b78 100644
--- a/arch/mips/kernel/sysirix.c
+++ b/arch/mips/kernel/sysirix.c
@@ -645,27 +645,7 @@ static inline void getitimer_real(struct itimerval *value)
 
 asmlinkage unsigned int irix_alarm(unsigned int seconds)
 {
-	struct itimerval it_new, it_old;
-	unsigned int oldalarm;
-
-	if (!seconds) {
-		getitimer_real(&it_old);
-		del_timer(&current->real_timer);
-	} else {
-		it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
-		it_new.it_value.tv_sec = seconds;
-		it_new.it_value.tv_usec = 0;
-		do_setitimer(ITIMER_REAL, &it_new, &it_old);
-	}
-	oldalarm = it_old.it_value.tv_sec;
-	/*
-	 * ehhh.. We can't return 0 if we have an alarm pending ...
-	 * And we'd better return too much than too little anyway
-	 */
-	if (it_old.it_value.tv_usec)
-		oldalarm++;
-
-	return oldalarm;
+	return alarm_setitimer(seconds);
 }
 
 asmlinkage int irix_pause(void)