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hrtimer: fix *rmtp handling in hrtimer_nanosleep()

Browse source 
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 04c227140f
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 <oleg@tv-sign.ru>
Cc: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Pavel Emelyanov <xemul@sw.ru>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Toyo Abe <toyoa@mvista.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

 include/linux/hrtimer.h |    2 -
 kernel/hrtimer.c        |   51 +++++++++++++++++++++++++-----------------------
 kernel/posix-timers.c   |   14 +------------
 3 files changed, 30 insertions(+), 37 deletions(-)
This commit is contained in:
Oleg Nesterov 2008-02-01 17:29:05 +03:00 committed by Thomas Gleixner
parent e13a2e61dd
commit 080344b988
3 changed files with 31 additions and 39 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
include/linux/hrtimer.h
View file

@ -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);

51
kernel/hrtimer.c
View file

@ -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 = &current_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);
}
/*

17
kernel/posix-timers.c
View file

@ -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