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From: Chris Friesen <cfriesen@nortelnetworks.com>
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To: Wichert Akkerman <wichert@wiggy.net>
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Subject: Re: sys_gettimeofday racy or not?
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Wichert Akkerman wrote:
> This just happened to catch my eye and it's probably perfectly
> valid, but if so please educate me on why it is. In kernel/time.c
> sys_gettimeofday() there is this code:
> 
>         if (unlikely(tz != NULL)) {
>                 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
>                         return -EFAULT;
>         }
> 
> what prevents sys_tz from being changed while this code runs?

Nothing at all.

I suspect most people don't worry about it, since its use is deprecated.  The 
man page for gettimeofday() says "The use of the timezone struct is obsolete".

Chris