Commit 238ec850 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Borislav Petkov (AMD)
Browse files

x86/srso: Fix return thunks in generated code 



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: fb3bd914 ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
parent d893832d

arch/x86/kernel/alternative.c

+1 −3
Original line number Diff line number Diff line
@@ -707,9 +707,7 @@ static int patch_return(void *addr, struct insn *insn, u8 *bytes) 
	int i = 0;



	/* Patch the custom return thunks... */

	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)) {

		i = JMP32_INSN_SIZE;

		__text_gen_insn(bytes, JMP32_INSN_OPCODE, addr, x86_return_thunk, i);

	} else {

arch/x86/kernel/cpu/bugs.c

+6 −0
Original line number Diff line number Diff line
@@ -2297,6 +2297,12 @@ 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