Re: Local DoS attack on i386

[Andre Tomt]

Nuno Monteiro wrote:
> The same fix should be applied to 2.4. I'm running locally a very
> hacked version of 2.4.22 with it and it survives that crash.c program.
>
> Here's the diff. Marcelo, please merge.
>
>
> --- linux-2.4.27-pre5/include/asm-i386/i387.h~fix-x86-clear_fpu-macro	2004-06-14 15:12:13.909059344 +0100
> +++ linux-2.4.27-pre5/include/asm-i386/i387.h	2004-06-14 15:12:45.970185312 +0100
> @@ -34,7 +34,7 @@ extern void kernel_fpu_begin(void);
>  
>  #define clear_fpu( tsk ) do { \
>  	if ( tsk->flags & PF_USEDFPU ) { \
> -		asm volatile("fwait"); \
> +		asm volatile("fnclex ; fwait"); \
>  		tsk->flags &= ~PF_USEDFPU; \
>  		stts(); \
>  	} \

You're missing x86-64.

Complete patches are up at <http://tomt.net/kernel/clear_fpu/> - these 
covers 2.4 and 2.6, plus i386 and x86-64.

But I guess Marcelo would want the x86-64 part to come through ak.

--
Cheers,
André Tomt
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