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x86/srso: Fix return thunks in generated code

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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@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josh Poimboeuf 2023-07-28 17:28:43 -05:00 committed by Greg Kroah-Hartman
parent c9ae63d773
commit c7f2cd0455
2 changed files with 7 additions and 3 deletions
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4
arch/x86/kernel/alternative.c
View File

@ -538,9 +538,7 @@ 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))
return -1;
bytes[i++] = RET_INSN_OPCODE;

6
arch/x86/kernel/cpu/bugs.c
View File

@ -2415,6 +2415,12 @@ 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