Re: [PATCH v3 2/6] x86/entry_64: Add VERW just before userspace transition

[Nikolay Borisov]

On 25.10.23 г. 23:52 ч., Pawan Gupta wrote:

<snip>

> @@ -1520,6 +1530,7 @@ SYM_CODE_START(ignore_sysret)
>   	UNWIND_HINT_END_OF_STACK
>   	ENDBR
>   	mov	$-ENOSYS, %eax
> +	CLEAR_CPU_BUFFERS

nit: Just out of curiosity is it really needed in this case or it's 
doesn for the sake of uniformity so that all ring3 transitions are 
indeed covered??

>   	sysretl
>   SYM_CODE_END(ignore_sysret)
>   #endif
> diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
> index 70150298f8bd..245697eb8485 100644
> --- a/arch/x86/entry/entry_64_compat.S
> +++ b/arch/x86/entry/entry_64_compat.S
> @@ -271,6 +271,7 @@ SYM_INNER_LABEL(entry_SYSRETL_compat_unsafe_stack, SYM_L_GLOBAL)
>   	xorl	%r9d, %r9d
>   	xorl	%r10d, %r10d
>   	swapgs
> +	CLEAR_CPU_BUFFERS
>   	sysretl
>   SYM_INNER_LABEL(entry_SYSRETL_compat_end, SYM_L_GLOBAL)
>   	ANNOTATE_NOENDBR