From 080344b98805553f9b01de0f59a41b1533036d8d Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 1 Feb 2008 17:29:05 +0300 Subject: [PATCH] hrtimer: fix *rmtp handling in hrtimer_nanosleep() Spotted by Pavel Emelyanov and Alexey Dobriyan. hrtimer_nanosleep() sets restart_block->arg1 = rmtp, but this rmtp points to the local variable which lives in the caller's stack frame. This means that if sys_restart_syscall() actually happens and it is interrupted as well, we don't update the user-space variable, but write into the already dead stack frame. Introduced by commit 04c227140fed77587432667a574b14736a06dd7f hrtimer: Rework hrtimer_nanosleep to make sys_compat_nanosleep easier Change the callers to pass "__user *rmtp" to hrtimer_nanosleep(), and change hrtimer_nanosleep() to use copy_to_user() to actually update *rmtp. Small problem remains. man 2 nanosleep states that *rtmp should be written if nanosleep() was interrupted (it says nothing whether it is OK to update *rmtp if nanosleep returns 0), but (with or without this patch) we can dirty *rem even if nanosleep() returns 0. NOTE: this patch doesn't change compat_sys_nanosleep(), because it has other bugs. Fixed by the next patch. Signed-off-by: Oleg Nesterov Cc: Alexey Dobriyan Cc: Michael Kerrisk Cc: Pavel Emelyanov Cc: Peter Zijlstra Cc: Toyo Abe Cc: Andrew Morton Signed-off-by: Thomas Gleixner include/linux/hrtimer.h | 2 - kernel/hrtimer.c | 51 +++++++++++++++++++++++++----------------------- kernel/posix-timers.c | 14 +------------ 3 files changed, 30 insertions(+), 37 deletions(-) --- include/linux/hrtimer.h | 2 +- kernel/hrtimer.c | 51 ++++++++++++++++++++++------------------- kernel/posix-timers.c | 17 +++----------- 3 files changed, 31 insertions(+), 39 deletions(-) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 600fc3bcf63..1ad56a7b2f7 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -316,7 +316,7 @@ static inline u64 hrtimer_forward_now(struct hrtimer *timer, /* Precise sleep: */ extern long hrtimer_nanosleep(struct timespec *rqtp, - struct timespec *rmtp, + struct timespec __user *rmtp, const enum hrtimer_mode mode, const clockid_t clockid); extern long hrtimer_nanosleep_restart(struct restart_block *restart_block); diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 668f3967eb3..355085f0896 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -1319,11 +1319,26 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod return t->task == NULL; } +static int update_rmtp(struct hrtimer *timer, struct timespec __user *rmtp) +{ + struct timespec rmt; + ktime_t rem; + + rem = ktime_sub(timer->expires, timer->base->get_time()); + if (rem.tv64 <= 0) + return 0; + rmt = ktime_to_timespec(rem); + + if (copy_to_user(rmtp, &rmt, sizeof(*rmtp))) + return -EFAULT; + + return 1; +} + long __sched hrtimer_nanosleep_restart(struct restart_block *restart) { struct hrtimer_sleeper t; - struct timespec *rmtp; - ktime_t time; + struct timespec __user *rmtp; restart->fn = do_no_restart_syscall; @@ -1333,12 +1348,11 @@ long __sched hrtimer_nanosleep_restart(struct restart_block *restart) if (do_nanosleep(&t, HRTIMER_MODE_ABS)) return 0; - rmtp = (struct timespec *)restart->arg1; + rmtp = (struct timespec __user *)restart->arg1; if (rmtp) { - time = ktime_sub(t.timer.expires, t.timer.base->get_time()); - if (time.tv64 <= 0) - return 0; - *rmtp = ktime_to_timespec(time); + int ret = update_rmtp(&t.timer, rmtp); + if (ret <= 0) + return ret; } restart->fn = hrtimer_nanosleep_restart; @@ -1347,12 +1361,11 @@ long __sched hrtimer_nanosleep_restart(struct restart_block *restart) return -ERESTART_RESTARTBLOCK; } -long hrtimer_nanosleep(struct timespec *rqtp, struct timespec *rmtp, +long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp, const enum hrtimer_mode mode, const clockid_t clockid) { struct restart_block *restart; struct hrtimer_sleeper t; - ktime_t rem; hrtimer_init(&t.timer, clockid, mode); t.timer.expires = timespec_to_ktime(*rqtp); @@ -1364,10 +1377,9 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec *rmtp, return -ERESTARTNOHAND; if (rmtp) { - rem = ktime_sub(t.timer.expires, t.timer.base->get_time()); - if (rem.tv64 <= 0) - return 0; - *rmtp = ktime_to_timespec(rem); + int ret = update_rmtp(&t.timer, rmtp); + if (ret <= 0) + return ret; } restart = ¤t_thread_info()->restart_block; @@ -1383,8 +1395,7 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec *rmtp, asmlinkage long sys_nanosleep(struct timespec __user *rqtp, struct timespec __user *rmtp) { - struct timespec tu, rmt; - int ret; + struct timespec tu; if (copy_from_user(&tu, rqtp, sizeof(tu))) return -EFAULT; @@ -1392,15 +1403,7 @@ sys_nanosleep(struct timespec __user *rqtp, struct timespec __user *rmtp) if (!timespec_valid(&tu)) return -EINVAL; - ret = hrtimer_nanosleep(&tu, rmtp ? &rmt : NULL, HRTIMER_MODE_REL, - CLOCK_MONOTONIC); - - if (ret && rmtp) { - if (copy_to_user(rmtp, &rmt, sizeof(*rmtp))) - return -EFAULT; - } - - return ret; + return hrtimer_nanosleep(&tu, rmtp, HRTIMER_MODE_REL, CLOCK_MONOTONIC); } /* diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c index ce268966007..022c9c3cee6 100644 --- a/kernel/posix-timers.c +++ b/kernel/posix-timers.c @@ -982,20 +982,9 @@ sys_clock_getres(const clockid_t which_clock, struct timespec __user *tp) static int common_nsleep(const clockid_t which_clock, int flags, struct timespec *tsave, struct timespec __user *rmtp) { - struct timespec rmt; - int ret; - - ret = hrtimer_nanosleep(tsave, rmtp ? &rmt : NULL, - flags & TIMER_ABSTIME ? - HRTIMER_MODE_ABS : HRTIMER_MODE_REL, - which_clock); - - if (ret && rmtp) { - if (copy_to_user(rmtp, &rmt, sizeof(*rmtp))) - return -EFAULT; - } - - return ret; + return hrtimer_nanosleep(tsave, rmtp, flags & TIMER_ABSTIME ? + HRTIMER_MODE_ABS : HRTIMER_MODE_REL, + which_clock); } asmlinkage long