[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, 13 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
index 17d956cebcb9..13fa72cac7d8 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -956,19 +956,7 @@ void do_timer(struct pt_regs *regs)
  */
 asmlinkage unsigned long sys_alarm(unsigned int seconds)
 {
-        struct itimerval it_new, it_old;
-        unsigned int oldalarm;
-
-        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 ((!oldalarm && it_old.it_value.tv_usec) || it_old.it_value.tv_usec >= 500000)
-                oldalarm++;
-        return oldalarm;
+        return alarm_setitimer(seconds);
 }
 
 #endif