提交 c08b8a49 编写于 作者: T Thomas Gleixner 提交者: Linus Torvalds

[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: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
上级 185ae6d7
......@@ -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
......
......@@ -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)
......
......@@ -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
......
......@@ -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);
......
......@@ -226,6 +226,43 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
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)
......
......@@ -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
......
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