From c08b8a49100715b20e6f7c997e992428b5e06078 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sat, 25 Mar 2006 03:06:33 -0800 Subject: [PATCH] [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/ia64/ia32/sys_ia32.c | 14 +------------- arch/mips/kernel/sysirix.c | 22 +--------------------- arch/x86_64/ia32/sys_ia32.c | 16 ++-------------- include/linux/time.h | 1 + kernel/itimer.c | 37 +++++++++++++++++++++++++++++++++++++ kernel/timer.c | 14 +------------- 6 files changed, 43 insertions(+), 61 deletions(-) diff --git a/arch/ia64/ia32/sys_ia32.c b/arch/ia64/ia32/sys_ia32.c index 70dba1f0e2ee..13e739e4c84d 100644 --- a/arch/ia64/ia32/sys_ia32.c +++ b/arch/ia64/ia32/sys_ia32.c @@ -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 diff --git a/arch/mips/kernel/sysirix.c b/arch/mips/kernel/sysirix.c index 0fc3730a294f..5407b784cd01 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(¤t->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) diff --git a/arch/x86_64/ia32/sys_ia32.c b/arch/x86_64/ia32/sys_ia32.c index 2bc55af95419..2b2d029f477c 100644 --- a/arch/x86_64/ia32/sys_ia32.c +++ b/arch/x86_64/ia32/sys_ia32.c @@ -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 diff --git a/include/linux/time.h b/include/linux/time.h index d9cdba54b789..bf0e785e2e03 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -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); diff --git a/kernel/itimer.c b/kernel/itimer.c index 379be2f8c84c..a2dc375927d8 100644 --- a/kernel/itimer.c +++ b/kernel/itimer.c @@ -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) 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 -- 2.20.1