Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765931AbYBANgA (ORCPT ); Fri, 1 Feb 2008 08:36:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757160AbYBANfk (ORCPT ); Fri, 1 Feb 2008 08:35:40 -0500 Received: from x346.tv-sign.ru ([89.108.83.215]:57833 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754609AbYBANfi (ORCPT ); Fri, 1 Feb 2008 08:35:38 -0500 Date: Fri, 1 Feb 2008 16:37:58 +0300 From: Oleg Nesterov To: Andrew Morton , Thomas Gleixner Cc: Alexey Dobriyan , Ingo Molnar , Michael Kerrisk , Pavel Emelyanov , Peter Zijlstra , Toyo Abe , linux-kernel@vger.kernel.org Subject: [PATCH 2/5] hrtimer_nanosleep: fix *rmtp handling Message-ID: <20080201133758.GA25623@tv-sign.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5412 Lines: 170 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 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 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/