Re: [tip:x86/vdso] x86/vdso32/syscall.S: Do not load __USER32_DS to %ss

[Borislav Petkov <bp@xxxxxxxxx>]

On Thu, Apr 23, 2015 at 11:56:21AM +0200, Denys Vlasenko wrote:
> The fix can look like this (untested):
> 
> 
> diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
> index 0c302d0..9f4c232 100644
> --- a/arch/x86/ia32/ia32entry.S
> +++ b/arch/x86/ia32/ia32entry.S
> @@ -198,6 +198,18 @@ sysexit_from_sys_call:
>  	 * with 'sysenter' and it uses the SYSENTER calling convention.
>  	 */
>  	andl    $~TS_COMPAT,ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
> +	/*
> +	 * On AMD, SYSRET32 does not modify %ss cached descriptor;

Ok, but doc says that in both long and compat mode, SYSRET does load
SS.sel with the value in MSR_STAR...

Hmmm.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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