Re: [PATCH] x86/entry/64: Fix CR3 restore order in paranoid_exit()

[Dave Hansen]

On 02/13/2018 06:27 PM, Josh Poimboeuf wrote:
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -1167,10 +1167,10 @@ ENTRY(paranoid_exit)
>  	UNWIND_HINT_REGS
>  	DISABLE_INTERRUPTS(CLBR_ANY)
>  	TRACE_IRQS_OFF_DEBUG
> +	RESTORE_CR3	scratch_reg=%r15 save_reg=%r14
>  	testl	%ebx, %ebx			/* swapgs needed? */
>  	jnz	.Lparanoid_exit_no_swapgs
>  	TRACE_IRQS_IRETQ
> -	RESTORE_CR3	scratch_reg=%rbx save_reg=%r14
>  	SWAPGS_UNSAFE_STACK
>  	jmp	.Lparanoid_exit_restore
>  .Lparanoid_exit_no_swapgs:

TRACE_IRQS_* call non-entry functions that are not mapped by the user
CR3.  How can this possibly work?  What am I missing?