linux-kernel - Re: [PATCH 3/5] compat_sys_nanosleep: fix *rmtp/restarts handling

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Date:	Fri, 1 Feb 2008 20:35:31 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alexey Dobriyan <adobriyan@...ru>,
	Pavel Emelyanov <xemul@...ru>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Toyo Abe <toyoa@...sta.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] compat_sys_nanosleep: fix *rmtp/restarts handling

On 02/01, Oleg Nesterov wrote:
>
> Hopefully this was the last bug, updated patch below.

That was a joke.

Contrary to my expectations, the patch didn't suffer (I hope) from the
buggy "PATCH 1/1". But it can be simplified a bit, no need to check ret
twice.


[PATCH 3/5] compat_sys_nanosleep: fix *rmtp/restarts handling

COMPLETELY UNTESTED.

Spotted by Pavel Emelyanov and Alexey Dobriyan.

compat_sys_nanosleep() implicitly uses hrtimer_nanosleep_restart(), this can't
work. Make a suitable compat_nanosleep_restart() helper.

Also, set ->addr_limit = KERNEL_DS before doing hrtimer_nanosleep(), this func
was changed by the previous patch and now takes the "__user *" parameter.

Thanks to Ingo Molnar for fixing the bug in this patch.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- MM/kernel/compat.c~x3_COMPAT_NANOSLEEP	2008-02-01 18:54:44.000000000 +0300
+++ MM/kernel/compat.c	2008-02-01 20:24:52.000000000 +0300
@@ -40,10 +40,35 @@ int put_compat_timespec(const struct tim
 			__put_user(ts->tv_nsec, &cts->tv_nsec)) ? -EFAULT : 0;
 }
 
+static long compat_nanosleep_restart(struct restart_block *restart)
+{
+	struct timespec rmt;
+	mm_segment_t oldfs;
+	long ret;
+	struct compat_timespec *rmtp = (struct compat_timespec *)(restart->arg1);
+
+	restart->arg1 = (unsigned long)&rmt;
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+	ret = hrtimer_nanosleep_restart(restart);
+	set_fs(oldfs);
+
+	if (ret) {
+		restart->fn = compat_nanosleep_restart;
+		restart->arg1 = (unsigned long)rmtp;
+
+		if (rmtp && put_compat_timespec(&rmt, rmtp))
+			return -EFAULT;
+	}
+
+	return ret;
+}
+
 asmlinkage long compat_sys_nanosleep(struct compat_timespec __user *rqtp,
 				     struct compat_timespec __user *rmtp)
 {
 	struct timespec tu, rmt;
+	mm_segment_t oldfs;
 	long ret;
 
 	if (get_compat_timespec(&tu, rqtp))
@@ -52,11 +77,20 @@ asmlinkage long compat_sys_nanosleep(str
 	if (!timespec_valid(&tu))
 		return -EINVAL;
 
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
 	ret = hrtimer_nanosleep(&tu, rmtp ? &rmt : NULL, HRTIMER_MODE_REL,
 				CLOCK_MONOTONIC);
+	set_fs(oldfs);
 
-	if (ret && rmtp) {
-		if (put_compat_timespec(&rmt, rmtp))
+	if (ret) {
+		struct restart_block *restart
+			= &current_thread_info()->restart_block;
+
+		restart->fn = compat_nanosleep_restart;
+		restart->arg1 = (unsigned long)rmtp;
+
+		if (rmtp && put_compat_timespec(&rmt, rmtp))
 			return -EFAULT;
 	}
 

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