* [PATCH] x86/entry: Remove UNTRAIN_RET from native_irq_return_ldt
@ 2022-07-13 19:58 Alexandre Chartre
2022-07-14 9:41 ` Peter Zijlstra
0 siblings, 1 reply; 2+ messages in thread
From: Alexandre Chartre @ 2022-07-13 19:58 UTC (permalink / raw)
To: peterz, bp, x86, linux-kernel
Cc: konrad.wilk, alexandre.chartre, boris.ostrovsky, ankur.a.arora,
maciej.szmigiero
UNTRAIN_RET is not needed in native_irq_return_ldt because ret untrain
has already be done at this point. In addition, when the RETBleed
mitigation is IBPB, UNTRAIN_RET clobbers several registers (AX, CX, DX)
so here it trashes user values which are in these registers.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
arch/x86/entry/entry_64.S | 1 -
1 file changed, 1 deletion(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 285e043a3e40..9953d966d124 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -727,7 +727,6 @@ native_irq_return_ldt:
pushq %rdi /* Stash user RDI */
swapgs /* to kernel GS */
SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi /* to kernel CR3 */
- UNTRAIN_RET
movq PER_CPU_VAR(espfix_waddr), %rdi
movq %rax, (0*8)(%rdi) /* user RAX */
--
2.31.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] x86/entry: Remove UNTRAIN_RET from native_irq_return_ldt
2022-07-13 19:58 [PATCH] x86/entry: Remove UNTRAIN_RET from native_irq_return_ldt Alexandre Chartre
@ 2022-07-14 9:41 ` Peter Zijlstra
0 siblings, 0 replies; 2+ messages in thread
From: Peter Zijlstra @ 2022-07-14 9:41 UTC (permalink / raw)
To: Alexandre Chartre
Cc: bp, x86, linux-kernel, konrad.wilk, boris.ostrovsky,
ankur.a.arora, maciej.szmigiero
On Wed, Jul 13, 2022 at 09:58:08PM +0200, Alexandre Chartre wrote:
> UNTRAIN_RET is not needed in native_irq_return_ldt because ret untrain
> has already be done at this point. In addition, when the RETBleed
> mitigation is IBPB, UNTRAIN_RET clobbers several registers (AX, CX, DX)
> so here it trashes user values which are in these registers.
>
> Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> arch/x86/entry/entry_64.S | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 285e043a3e40..9953d966d124 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -727,7 +727,6 @@ native_irq_return_ldt:
> pushq %rdi /* Stash user RDI */
> swapgs /* to kernel GS */
> SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi /* to kernel CR3 */
> - UNTRAIN_RET
>
> movq PER_CPU_VAR(espfix_waddr), %rdi
> movq %rax, (0*8)(%rdi) /* user RAX */
> --
> 2.31.1
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2022-07-14 9:42 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-07-13 19:58 [PATCH] x86/entry: Remove UNTRAIN_RET from native_irq_return_ldt Alexandre Chartre
2022-07-14 9:41 ` Peter Zijlstra
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox