From b155f54a92b0c8fe62eb5b45d062613626428fc5 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 28 Jul 2023 17:28:43 -0500 Subject: [PATCH] x86/srso: Fix return thunks in generated code 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 Signed-off-by: Borislav Petkov (AMD) Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/alternative.c | 4 +--- arch/x86/kernel/cpu/bugs.c | 6 ++++++ 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index d516781e5756..f615e0cb6d93 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -590,9 +590,7 @@ static int patch_return(void *addr, struct insn *insn, u8 *bytes) { 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)) { if (x86_return_thunk == __x86_return_thunk) return -1; diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 1ba0e1c0650d..9ab38d04f686 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -2444,6 +2444,12 @@ static void __init srso_select_mitigation(void) 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