Commit 72c70f48 authored by Breno Leitao's avatar Breno Leitao Committed by Borislav Petkov (AMD)
Browse files

x86/bugs: Add a separate config for Spectre V2 



Currently, the CONFIG_SPECULATION_MITIGATIONS is halfway populated,
where some mitigations have entries in Kconfig, and they could be
modified, while others mitigations do not have Kconfig entries, and
could not be controlled at build time.

Create an entry for the Spectre V2 CPU mitigation under
CONFIG_SPECULATION_MITIGATIONS. This allow users to enable or disable
it at compilation time.

Signed-off-by: default avatarBreno Leitao <leitao@debian.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20240729164105.554296-9-leitao@debian.org
parent a0b02e3f

arch/x86/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -2716,6 +2716,18 @@ config MITIGATION_SPECTRE_V1 
	  memory access bounds check.

	  See also <file:Documentation/admin-guide/hw-vuln/spectre.rst>



config MITIGATION_SPECTRE_V2

	bool "Mitigate SPECTRE V2 hardware bug"

	default y

	help

	  Enable mitigation for Spectre V2 (Branch Target Injection). Spectre

	  V2 is a class of side channel attacks that takes advantage of

	  indirect branch predictors inside the processor. In Spectre variant 2

	  attacks, the attacker can steer speculative indirect branches in the

	  victim to gadget code by poisoning the branch target buffer of a CPU

	  used for predicting indirect branch addresses.

	  See also <file:Documentation/admin-guide/hw-vuln/spectre.rst>



config MITIGATION_SRBDS

	bool "Mitigate Special Register Buffer Data Sampling (SRBDS) hardware bug"

	depends on CPU_SUP_INTEL

arch/x86/kernel/cpu/bugs.c

+5 −4
Original line number Diff line number Diff line
@@ -1452,17 +1452,18 @@ static void __init spec_v2_print_cond(const char *reason, bool secure) 


static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)

{

	enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;

	enum spectre_v2_mitigation_cmd cmd;

	char arg[20];

	int ret, i;



	cmd = IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ?  SPECTRE_V2_CMD_AUTO : SPECTRE_V2_CMD_NONE;

	if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") ||

	    cpu_mitigations_off())

		return SPECTRE_V2_CMD_NONE;



	ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));

	if (ret < 0)

		return SPECTRE_V2_CMD_AUTO;

		return cmd;



	for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {

		if (!match_option(arg, ret, mitigation_options[i].option))
@@ -1472,8 +1473,8 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) 
	}



	if (i >= ARRAY_SIZE(mitigation_options)) {

		pr_err("unknown option (%s). Switching to AUTO select\n", arg);

		return SPECTRE_V2_CMD_AUTO;

		pr_err("unknown option (%s). Switching to default mode\n", arg);

		return cmd;

	}



	if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||