Commit ff54ae73 authored by David Kaplan's avatar David Kaplan Committed by Ingo Molnar
Browse files

x86/bugs: Use IBPB for retbleed if used by SRSO 



If spec_rstack_overflow=ibpb then this mitigates retbleed as well.  This
is relevant for AMD Zen1 and Zen2 CPUs which are vulnerable to both bugs.

Signed-off-by: default avatarDavid Kaplan <david.kaplan@amd.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250625155805.600376-3-david.kaplan@amd.com
parent 1fd5eb02

arch/x86/kernel/cpu/bugs.c

+19 −15
Original line number Diff line number Diff line
@@ -1171,6 +1171,21 @@ static enum retbleed_mitigation retbleed_mitigation __ro_after_init = 


static int __ro_after_init retbleed_nosmt = false;



enum srso_mitigation {

	SRSO_MITIGATION_NONE,

	SRSO_MITIGATION_AUTO,

	SRSO_MITIGATION_UCODE_NEEDED,

	SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,

	SRSO_MITIGATION_MICROCODE,

	SRSO_MITIGATION_NOSMT,

	SRSO_MITIGATION_SAFE_RET,

	SRSO_MITIGATION_IBPB,

	SRSO_MITIGATION_IBPB_ON_VMEXIT,

	SRSO_MITIGATION_BP_SPEC_REDUCE,

};



static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_AUTO;



static int __init retbleed_parse_cmdline(char *str)

{

	if (!str)
@@ -1280,6 +1295,10 @@ static void __init retbleed_update_mitigation(void) 
	if (its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF)

		retbleed_mitigation = RETBLEED_MITIGATION_STUFF;



	/* If SRSO is using IBPB, that works for retbleed too */

	if (srso_mitigation == SRSO_MITIGATION_IBPB)

		retbleed_mitigation = RETBLEED_MITIGATION_IBPB;



	if (retbleed_mitigation == RETBLEED_MITIGATION_STUFF &&

	    !cdt_possible(spectre_v2_enabled)) {

		pr_err("WARNING: retbleed=stuff depends on retpoline\n");
@@ -2845,19 +2864,6 @@ early_param("l1tf", l1tf_cmdline); 
#undef pr_fmt

#define pr_fmt(fmt)	"Speculative Return Stack Overflow: " fmt



enum srso_mitigation {

	SRSO_MITIGATION_NONE,

	SRSO_MITIGATION_AUTO,

	SRSO_MITIGATION_UCODE_NEEDED,

	SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,

	SRSO_MITIGATION_MICROCODE,

	SRSO_MITIGATION_NOSMT,

	SRSO_MITIGATION_SAFE_RET,

	SRSO_MITIGATION_IBPB,

	SRSO_MITIGATION_IBPB_ON_VMEXIT,

	SRSO_MITIGATION_BP_SPEC_REDUCE,

};



static const char * const srso_strings[] = {

	[SRSO_MITIGATION_NONE]			= "Vulnerable",

	[SRSO_MITIGATION_UCODE_NEEDED]		= "Vulnerable: No microcode",
@@ -2870,8 +2876,6 @@ static const char * const srso_strings[] = { 
	[SRSO_MITIGATION_BP_SPEC_REDUCE]	= "Mitigation: Reduced Speculation"

};



static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_AUTO;



static int __init srso_parse_cmdline(char *str)

{

	if (!str)