Commit c08b8a49 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
Browse files

[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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 185ae6d7

arch/ia64/ia32/sys_ia32.c

+1 −13
Original line number Diff line number Diff line
@@ -1166,19 +1166,7 @@ put_tv32 (struct compat_timeval __user *o, struct timeval *i) 
asmlinkage unsigned long

sys32_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 (it_old.it_value.tv_usec)

		oldalarm++;

	return oldalarm;

	return alarm_setitimer(seconds);

}



/* Translations due to time_t size differences.  Which affects all

arch/mips/kernel/sysirix.c

+1 −21
Original line number Diff line number Diff line
@@ -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)

arch/x86_64/ia32/sys_ia32.c

+2 −14
Original line number Diff line number Diff line
@@ -430,24 +430,12 @@ put_tv32(struct compat_timeval __user *o, struct timeval *i) 
	return err; 

}



extern int do_setitimer(int which, struct itimerval *, struct itimerval *);

extern unsigned int alarm_setitimer(unsigned int seconds);



asmlinkage long

sys32_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 (it_old.it_value.tv_usec)

		oldalarm++;

	return oldalarm;

	return alarm_setitimer(seconds);

}



/* Translations due to time_t size differences.  Which affects all

include/linux/time.h

+1 −0
Original line number Diff line number Diff line
@@ -101,6 +101,7 @@ extern long do_utimes(int dfd, char __user *filename, struct timeval *times); 
struct itimerval;

extern int do_setitimer(int which, struct itimerval *value,

			struct itimerval *ovalue);

extern unsigned int alarm_setitimer(unsigned int seconds);

extern int do_getitimer(int which, struct itimerval *value);

extern void getnstimeofday(struct timespec *tv);

kernel/itimer.c

+37 −0
Original line number Diff line number Diff line
@@ -226,6 +226,43 @@ again: 
	return 0;

}



/**

 * alarm_setitimer - set alarm in seconds

 *

 * @seconds:	number of seconds until alarm

 *		0 disables the alarm

 *

 * Returns the remaining time in seconds of a pending timer or 0 when

 * the timer is not active.

 *

 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid

 * negative timeval settings which would cause immediate expiry.

 */

unsigned int alarm_setitimer(unsigned int seconds)

{

	struct itimerval it_new, it_old;



#if BITS_PER_LONG < 64

	if (seconds > INT_MAX)

		seconds = INT_MAX;

#endif

	it_new.it_value.tv_sec = seconds;

	it_new.it_value.tv_usec = 0;

	it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;



	do_setitimer(ITIMER_REAL, &it_new, &it_old);



	/*

	 * 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_sec && it_old.it_value.tv_usec) ||

	      it_old.it_value.tv_usec >= 500000)

		it_old.it_value.tv_sec++;



	return it_old.it_value.tv_sec;

}



asmlinkage long sys_setitimer(int which,

			      struct itimerval __user *value,

			      struct itimerval __user *ovalue)

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