Re: [patch 4/8] x86/fpu: Limit xstate copy size in xstateregs_set()

[Borislav Petkov]

On Wed, Jun 02, 2021 at 11:55:47AM +0200, Thomas Gleixner wrote:
> If the count argument is larger than the xstate size, this will happily
> copy beyond the end of xstate.
> 
> Fixes: 91c3dba7dbc1 ("x86/fpu/xstate: Fix PTRACE frames for XSAVES")
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>  arch/x86/kernel/fpu/regset.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/arch/x86/kernel/fpu/regset.c
> +++ b/arch/x86/kernel/fpu/regset.c
> @@ -117,7 +117,7 @@ int xstateregs_set(struct task_struct *t
>  	/*
>  	 * A whole standard-format XSAVE buffer is needed:
>  	 */
> -	if ((pos != 0) || (count < fpu_user_xstate_size))
> +	if (pos != 0 || count != fpu_user_xstate_size)
>  		return -EFAULT;
>  
>  	xsave = &fpu->state.xsave;

Looking at this one, I guess it and all the CC:stable ones should be at
the beginning of the set so that they go to Linus now...

-- 
Regards/Gruss,
    Boris.

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