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

[Oleg Nesterov]

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 <[EMAIL PROTECTED]>

--- 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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