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Date: Fri, 1 Feb 2008 14:49:03 +0100 (CET)
From: Thomas Gleixner <tglx@...utronix.de>
To: Oleg Nesterov <oleg@...sign.ru>
cc: Andrew Morton <akpm@...ux-foundation.org>,
Alexey Dobriyan <adobriyan@...ru>, Ingo Molnar <mingo@...e.hu>,
Michael Kerrisk <mtk.manpages@...glemail.com>,
Pavel Emelyanov <xemul@...ru>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Toyo Abe <toyoa@...sta.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] hrtimer_nanosleep: fix *rmtp handling
On Fri, 1 Feb 2008, Oleg Nesterov wrote:
> Spotted by Pavel Emelyanov and Alexey Dobriyan.
Doh, yes. This was introduced by:
04c227140fed77587432667a574b14736a06dd7f
I did not notice, when I picked up the patch.
Thanks for fixing this,
tglx
> 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 the user-space variable, but write into the already dead stack frame.
>
> 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 disty *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 <oleg@...sign.ru>
>
> include/linux/hrtimer.h | 2 -
> kernel/hrtimer.c | 51 +++++++++++++++++++++++++-----------------------
> kernel/posix-timers.c | 14 +------------
> 3 files changed, 30 insertions(+), 37 deletions(-)
>
> --- MM/include/linux/hrtimer.h~HRT_RMTP 2008-01-27 17:07:39.000000000 +0300
> +++ MM/include/linux/hrtimer.h 2008-01-31 14:01:53.000000000 +0300
> @@ -313,7 +313,7 @@ static inline u64 hrtimer_forward_now(st
>
> /* 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);
> --- MM/kernel/hrtimer.c~HRT_RMTP 2008-02-01 13:43:52.000000000 +0300
> +++ MM/kernel/hrtimer.c 2008-02-01 13:56:44.000000000 +0300
> @@ -1317,11 +1317,26 @@ static int __sched do_nanosleep(struct h
> 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;
>
> @@ -1331,12 +1346,11 @@ long __sched hrtimer_nanosleep_restart(s
> 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;
> @@ -1345,12 +1359,11 @@ long __sched hrtimer_nanosleep_restart(s
> 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);
> @@ -1362,10 +1375,9 @@ long hrtimer_nanosleep(struct timespec *
> return -EINTR;
>
> 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;
> @@ -1381,8 +1393,7 @@ long hrtimer_nanosleep(struct timespec *
> 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;
> @@ -1390,15 +1401,7 @@ sys_nanosleep(struct timespec __user *rq
> 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);
> }
>
> /*
> --- MM/kernel/posix-timers.c~HRT_RMTP 2008-01-27 17:07:40.000000000 +0300
> +++ MM/kernel/posix-timers.c 2008-02-01 13:18:51.000000000 +0300
> @@ -982,20 +982,10 @@ sys_clock_getres(const clockid_t which_c
> 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,
> + return hrtimer_nanosleep(tsave, rmtp,
> flags & TIMER_ABSTIME ?
> - HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
> + HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
> which_clock);
> -
> - if (ret && rmtp) {
> - if (copy_to_user(rmtp, &rmt, sizeof(*rmtp)))
> - return -EFAULT;
> - }
> -
> - return ret;
> }
>
> asmlinkage long
>
--
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