This is a note to let you know that I've just added the patch titled
x86/srso: Fix return thunks in generated code
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-srso-fix-return-thunks-in-generated-code.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b07ad30ad7d510c3bc0398a8b4ee98293bca7c77 Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Fri, 28 Jul 2023 17:28:43 -0500
Subject: x86/srso: Fix return thunks in generated code
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Upstream commit: 238ec850b95a02dcdff3edc86781aa913549282f
Set X86_FEATURE_RETHUNK when enabling the SRSO mitigation so that
generated code (e.g., ftrace, static call, eBPF) generates "jmp
__x86_return_thunk" instead of RET.
[ bp: Add a comment. ]
Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/alternative.c | 4 +---
arch/x86/kernel/cpu/bugs.c | 6 ++++++
2 files changed, 7 insertions(+), 3 deletions(-)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -678,9 +678,7 @@ static int patch_return(void *addr, stru
{
int i = 0;
- if (cpu_feature_enabled(X86_FEATURE_RETHUNK) ||
- cpu_feature_enabled(X86_FEATURE_SRSO) ||
- cpu_feature_enabled(X86_FEATURE_SRSO_ALIAS))
+ if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
return -1;
bytes[i++] = RET_INSN_OPCODE;
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2345,6 +2345,12 @@ static void __init srso_select_mitigatio
case SRSO_CMD_SAFE_RET:
if (IS_ENABLED(CONFIG_CPU_SRSO)) {
+ /*
+ * Enable the return thunk for generated code
+ * like ftrace, static_call, etc.
+ */
+ setup_force_cpu_cap(X86_FEATURE_RETHUNK);
+
if (boot_cpu_data.x86 == 0x19)
setup_force_cpu_cap(X86_FEATURE_SRSO_ALIAS);
else
Patches currently in stable-queue which might be from jpoimboe@xxxxxxxxxx are
queue-5.10/x86-speculation-add-kconfig-option-for-gds.patch
queue-5.10/x86-speculation-add-gather-data-sampling-mitigation.patch
queue-5.10/kvm-add-gds_no-support-to-kvm.patch
queue-5.10/x86-speculation-add-force-option-to-gds-mitigation.patch
queue-5.10/x86-srso-fix-return-thunks-in-generated-code.patch
