Merge tag 'x86_bugs_for_v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 spectre fixes from Borislav Petkov:

 - Mitigate Spectre v2-type Branch History Buffer attacks on machines
   which support eIBRS, i.e., the hardware-assisted speculation
   restriction after it has been shown that such machines are vulnerable
   even with the hardware mitigation.

 - Do not use the default LFENCE-based Spectre v2 mitigation on AMD as
   it is insufficient to mitigate such attacks. Instead, switch to
   retpolines on all AMD by default.

 - Update the docs and add some warnings for the obviously vulnerable
   cmdline configurations.

* tag 'x86_bugs_for_v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/speculation: Warn about eIBRS + LFENCE + Unprivileged eBPF + SMT
  x86/speculation: Warn about Spectre v2 LFENCE mitigation
  x86/speculation: Update link to AMD speculation whitepaper
  x86/speculation: Use generic retpoline by default on AMD
  x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting
  Documentation/hw-vuln: Update spectre doc
  x86/speculation: Add eIBRS + Retpoline options
  x86/speculation: Rename RETPOLINE_AMD to RETPOLINE_LFENCE

Documentation/admin-guide/hw-vuln/spectre.rst

@@ -60,8 +60,8 @@ privileged data touched during the speculative execution.
 Spectre variant 1 attacks take advantage of speculative execution of
 conditional branches, while Spectre variant 2 attacks use speculative
 execution of indirect branches to leak privileged memory.
-See :ref:`[1] <spec_ref1>` :ref:`[5] <spec_ref5>` :ref:`[7] <spec_ref7>`
-:ref:`[10] <spec_ref10>` :ref:`[11] <spec_ref11>`.
+See :ref:`[1] <spec_ref1>` :ref:`[5] <spec_ref5>` :ref:`[6] <spec_ref6>`
+:ref:`[7] <spec_ref7>` :ref:`[10] <spec_ref10>` :ref:`[11] <spec_ref11>`.
 
 Spectre variant 1 (Bounds Check Bypass)
 ---------------------------------------
@@ -131,6 +131,19 @@ steer its indirect branch speculations to gadget code, and measure the
 speculative execution's side effects left in level 1 cache to infer the
 victim's data.
 
+Yet another variant 2 attack vector is for the attacker to poison the
+Branch History Buffer (BHB) to speculatively steer an indirect branch
+to a specific Branch Target Buffer (BTB) entry, even if the entry isn't
+associated with the source address of the indirect branch. Specifically,
+the BHB might be shared across privilege levels even in the presence of
+Enhanced IBRS.
+
+Currently the only known real-world BHB attack vector is via
+unprivileged eBPF. Therefore, it's highly recommended to not enable
+unprivileged eBPF, especially when eIBRS is used (without retpolines).
+For a full mitigation against BHB attacks, it's recommended to use
+retpolines (or eIBRS combined with retpolines).
+
 Attack scenarios
 ----------------
 
@@ -364,13 +377,15 @@ The possible values in this file are:
 
   - Kernel status:
 
-  ====================================  =================================
+  ========================================  =================================
   'Not affected'                            The processor is not vulnerable
-  'Vulnerable'                          Vulnerable, no mitigation
-  'Mitigation: Full generic retpoline'  Software-focused mitigation
-  'Mitigation: Full AMD retpoline'      AMD-specific software mitigation
+  'Mitigation: None'                        Vulnerable, no mitigation
+  'Mitigation: Retpolines'                  Use Retpoline thunks
+  'Mitigation: LFENCE'                      Use LFENCE instructions
   'Mitigation: Enhanced IBRS'               Hardware-focused mitigation
-  ====================================  =================================
+  'Mitigation: Enhanced IBRS + Retpolines'  Hardware-focused + Retpolines
+  'Mitigation: Enhanced IBRS + LFENCE'      Hardware-focused + LFENCE
+  ========================================  =================================
 
   - Firmware status: Show if Indirect Branch Restricted Speculation (IBRS) is
     used to protect against Spectre variant 2 attacks when calling firmware (x86 only).
@@ -583,12 +598,13 @@ kernel command line.
 
 		Specific mitigations can also be selected manually:
 
-		retpoline
-					replace indirect branches
-		retpoline,generic
-					google's original retpoline
-		retpoline,amd
-					AMD-specific minimal thunk
+                retpoline               auto pick between generic,lfence
+                retpoline,generic       Retpolines
+                retpoline,lfence        LFENCE; indirect branch
+                retpoline,amd           alias for retpoline,lfence
+                eibrs                   enhanced IBRS
+                eibrs,retpoline         enhanced IBRS + Retpolines
+                eibrs,lfence            enhanced IBRS + LFENCE
 
 		Not specifying this option is equivalent to
 		spectre_v2=auto.
@@ -599,7 +615,7 @@ kernel command line.
 		spectre_v2=off. Spectre variant 1 mitigations
 		cannot be disabled.
 
-For spectre_v2_user see :doc:`/admin-guide/kernel-parameters`.
+For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt
 
 Mitigation selection guide
 --------------------------
@@ -681,7 +697,7 @@ AMD white papers:
 
 .. _spec_ref6:
 
-[6] `Software techniques for managing speculation on AMD processors <https://developer.amd.com/wp-content/resources/90343-B_SoftwareTechniquesforManagingSpeculation_WP_7-18Update_FNL.pdf>`_.
+[6] `Software techniques for managing speculation on AMD processors <https://developer.amd.com/wp-content/resources/Managing-Speculation-on-AMD-Processors.pdf>`_.
 
 ARM white papers:
 

Documentation/admin-guide/kernel-parameters.txt

@@ -5361,8 +5361,12 @@
 			Specific mitigations can also be selected manually:
 
 			retpoline	  - replace indirect branches
-			retpoline,generic - google's original retpoline
-			retpoline,amd     - AMD-specific minimal thunk
+			retpoline,generic - Retpolines
+			retpoline,lfence  - LFENCE; indirect branch
+			retpoline,amd     - alias for retpoline,lfence
+			eibrs		  - enhanced IBRS
+			eibrs,retpoline   - enhanced IBRS + Retpolines
+			eibrs,lfence      - enhanced IBRS + LFENCE
 
 			Not specifying this option is equivalent to
 			spectre_v2=auto.

arch/x86/include/asm/cpufeatures.h

@@ -204,7 +204,7 @@
 /* FREE!                                ( 7*32+10) */
 #define X86_FEATURE_PTI			( 7*32+11) /* Kernel Page Table Isolation enabled */
 #define X86_FEATURE_RETPOLINE		( 7*32+12) /* "" Generic Retpoline mitigation for Spectre variant 2 */
-#define X86_FEATURE_RETPOLINE_AMD	( 7*32+13) /* "" AMD Retpoline mitigation for Spectre variant 2 */
+#define X86_FEATURE_RETPOLINE_LFENCE	( 7*32+13) /* "" Use LFENCE for Spectre variant 2 */
 #define X86_FEATURE_INTEL_PPIN		( 7*32+14) /* Intel Processor Inventory Number */
 #define X86_FEATURE_CDP_L2		( 7*32+15) /* Code and Data Prioritization L2 */
 #define X86_FEATURE_MSR_SPEC_CTRL	( 7*32+16) /* "" MSR SPEC_CTRL is implemented */

arch/x86/include/asm/nospec-branch.h

@@ -84,7 +84,7 @@
 #ifdef CONFIG_RETPOLINE
 	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
 		      __stringify(jmp __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \
-		      __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_AMD
+		      __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE
 #else
 	jmp	*%\reg
 #endif
@@ -94,7 +94,7 @@
 #ifdef CONFIG_RETPOLINE
 	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; call *%\reg), \
 		      __stringify(call __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \
-		      __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *%\reg), X86_FEATURE_RETPOLINE_AMD
+		      __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *%\reg), X86_FEATURE_RETPOLINE_LFENCE
 #else
 	call	*%\reg
 #endif
@@ -146,7 +146,7 @@ extern retpoline_thunk_t __x86_indirect_thunk_array[];
 	"lfence;\n"						\
 	ANNOTATE_RETPOLINE_SAFE					\
 	"call *%[thunk_target]\n",				\
-	X86_FEATURE_RETPOLINE_AMD)
+	X86_FEATURE_RETPOLINE_LFENCE)
 
 # define THUNK_TARGET(addr) [thunk_target] "r" (addr)
 
@@ -176,7 +176,7 @@ extern retpoline_thunk_t __x86_indirect_thunk_array[];
 	"lfence;\n"						\
 	ANNOTATE_RETPOLINE_SAFE					\
 	"call *%[thunk_target]\n",				\
-	X86_FEATURE_RETPOLINE_AMD)
+	X86_FEATURE_RETPOLINE_LFENCE)
 
 # define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
 #endif
@@ -188,9 +188,11 @@ extern retpoline_thunk_t __x86_indirect_thunk_array[];
 /* The Spectre V2 mitigation variants */
 enum spectre_v2_mitigation {
 	SPECTRE_V2_NONE,
-	SPECTRE_V2_RETPOLINE_GENERIC,
-	SPECTRE_V2_RETPOLINE_AMD,
-	SPECTRE_V2_IBRS_ENHANCED,
+	SPECTRE_V2_RETPOLINE,
+	SPECTRE_V2_LFENCE,
+	SPECTRE_V2_EIBRS,
+	SPECTRE_V2_EIBRS_RETPOLINE,
+	SPECTRE_V2_EIBRS_LFENCE,
 };
 
 /* The indirect branch speculation control variants */

arch/x86/kernel/alternative.c

@@ -389,7 +389,7 @@ static int emit_indirect(int op, int reg, u8 *bytes)
  *
  *   CALL *%\reg
  *
- * It also tries to inline spectre_v2=retpoline,amd when size permits.
+ * It also tries to inline spectre_v2=retpoline,lfence when size permits.
  */
 static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes)
 {
@@ -407,7 +407,7 @@ static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes)
 	BUG_ON(reg == 4);
 
 	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE) &&
-	    !cpu_feature_enabled(X86_FEATURE_RETPOLINE_AMD))
+	    !cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE))
 		return -1;
 
 	op = insn->opcode.bytes[0];
@@ -438,9 +438,9 @@ static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes)
 	}
 
 	/*
-	 * For RETPOLINE_AMD: prepend the indirect CALL/JMP with an LFENCE.
+	 * For RETPOLINE_LFENCE: prepend the indirect CALL/JMP with an LFENCE.
 	 */
-	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_AMD)) {
+	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) {
 		bytes[i++] = 0x0f;
 		bytes[i++] = 0xae;
 		bytes[i++] = 0xe8; /* LFENCE */

arch/x86/kernel/cpu/bugs.c

@@ -16,6 +16,7 @@
 #include <linux/prctl.h>
 #include <linux/sched/smt.h>
 #include <linux/pgtable.h>
+#include <linux/bpf.h>
 
 #include <asm/spec-ctrl.h>
 #include <asm/cmdline.h>
@@ -650,6 +651,32 @@ static inline const char *spectre_v2_module_string(void)
 static inline const char *spectre_v2_module_string(void) { return ""; }
 #endif
 
+#define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n"
+#define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n"
+#define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n"
+
+#ifdef CONFIG_BPF_SYSCALL
+void unpriv_ebpf_notify(int new_state)
+{
+	if (new_state)
+		return;
+
+	/* Unprivileged eBPF is enabled */
+
+	switch (spectre_v2_enabled) {
+	case SPECTRE_V2_EIBRS:
+		pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
+		break;
+	case SPECTRE_V2_EIBRS_LFENCE:
+		if (sched_smt_active())
+			pr_err(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
+		break;
+	default:
+		break;
+	}
+}
+#endif
+
 static inline bool match_option(const char *arg, int arglen, const char *opt)
 {
 	int len = strlen(opt);
@@ -664,7 +691,10 @@ enum spectre_v2_mitigation_cmd {
 	SPECTRE_V2_CMD_FORCE,
 	SPECTRE_V2_CMD_RETPOLINE,
 	SPECTRE_V2_CMD_RETPOLINE_GENERIC,
-	SPECTRE_V2_CMD_RETPOLINE_AMD,
+	SPECTRE_V2_CMD_RETPOLINE_LFENCE,
+	SPECTRE_V2_CMD_EIBRS,
+	SPECTRE_V2_CMD_EIBRS_RETPOLINE,
+	SPECTRE_V2_CMD_EIBRS_LFENCE,
 };
 
 enum spectre_v2_user_cmd {
@@ -737,6 +767,13 @@ spectre_v2_parse_user_cmdline(enum spectre_v2_mitigation_cmd v2_cmd)
 	return SPECTRE_V2_USER_CMD_AUTO;
 }
 
+static inline bool spectre_v2_in_eibrs_mode(enum spectre_v2_mitigation mode)
+{
+	return (mode == SPECTRE_V2_EIBRS ||
+		mode == SPECTRE_V2_EIBRS_RETPOLINE ||
+		mode == SPECTRE_V2_EIBRS_LFENCE);
+}
+
 static void __init
 spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 {
@@ -804,7 +841,7 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 	 */
 	if (!boot_cpu_has(X86_FEATURE_STIBP) ||
 	    !smt_possible ||
-	    spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+	    spectre_v2_in_eibrs_mode(spectre_v2_enabled))
 		return;
 
 	/*
@@ -824,9 +861,11 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 
 static const char * const spectre_v2_strings[] = {
 	[SPECTRE_V2_NONE]			= "Vulnerable",
-	[SPECTRE_V2_RETPOLINE_GENERIC]		= "Mitigation: Full generic retpoline",
-	[SPECTRE_V2_RETPOLINE_AMD]		= "Mitigation: Full AMD retpoline",
-	[SPECTRE_V2_IBRS_ENHANCED]		= "Mitigation: Enhanced IBRS",
+	[SPECTRE_V2_RETPOLINE]			= "Mitigation: Retpolines",
+	[SPECTRE_V2_LFENCE]			= "Mitigation: LFENCE",
+	[SPECTRE_V2_EIBRS]			= "Mitigation: Enhanced IBRS",
+	[SPECTRE_V2_EIBRS_LFENCE]		= "Mitigation: Enhanced IBRS + LFENCE",
+	[SPECTRE_V2_EIBRS_RETPOLINE]		= "Mitigation: Enhanced IBRS + Retpolines",
 };
 
 static const struct {
@@ -837,8 +876,12 @@ static const struct {
 	{ "off",		SPECTRE_V2_CMD_NONE,		  false },
 	{ "on",			SPECTRE_V2_CMD_FORCE,		  true  },
 	{ "retpoline",		SPECTRE_V2_CMD_RETPOLINE,	  false },
-	{ "retpoline,amd",	SPECTRE_V2_CMD_RETPOLINE_AMD,	  false },
+	{ "retpoline,amd",	SPECTRE_V2_CMD_RETPOLINE_LFENCE,  false },
+	{ "retpoline,lfence",	SPECTRE_V2_CMD_RETPOLINE_LFENCE,  false },
 	{ "retpoline,generic",	SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
+	{ "eibrs",		SPECTRE_V2_CMD_EIBRS,		  false },
+	{ "eibrs,lfence",	SPECTRE_V2_CMD_EIBRS_LFENCE,	  false },
+	{ "eibrs,retpoline",	SPECTRE_V2_CMD_EIBRS_RETPOLINE,	  false },
 	{ "auto",		SPECTRE_V2_CMD_AUTO,		  false },
 };
 
@@ -875,10 +918,30 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 	}
 
 	if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
-	     cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
-	     cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
+	     cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
+	     cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
 	    !IS_ENABLED(CONFIG_RETPOLINE)) {
-		pr_err("%s selected but not compiled in. Switching to AUTO select\n", mitigation_options[i].option);
+		pr_err("%s selected but not compiled in. Switching to AUTO select\n",
+		       mitigation_options[i].option);
+		return SPECTRE_V2_CMD_AUTO;
+	}
+
+	if ((cmd == SPECTRE_V2_CMD_EIBRS ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
+	    !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
+		pr_err("%s selected but CPU doesn't have eIBRS. Switching to AUTO select\n",
+		       mitigation_options[i].option);
+		return SPECTRE_V2_CMD_AUTO;
+	}
+
+	if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) &&
+	    !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
+		pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n",
+		       mitigation_options[i].option);
 		return SPECTRE_V2_CMD_AUTO;
 	}
 
@@ -887,6 +950,16 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 	return cmd;
 }
 
+static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void)
+{
+	if (!IS_ENABLED(CONFIG_RETPOLINE)) {
+		pr_err("Kernel not compiled with retpoline; no mitigation available!");
+		return SPECTRE_V2_NONE;
+	}
+
+	return SPECTRE_V2_RETPOLINE;
+}
+
 static void __init spectre_v2_select_mitigation(void)
 {
 	enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
@@ -907,49 +980,64 @@ static void __init spectre_v2_select_mitigation(void)
 	case SPECTRE_V2_CMD_FORCE:
 	case SPECTRE_V2_CMD_AUTO:
 		if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
-			mode = SPECTRE_V2_IBRS_ENHANCED;
-			/* Force it so VMEXIT will restore correctly */
-			x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
-			wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
-			goto specv2_set_mode;
+			mode = SPECTRE_V2_EIBRS;
+			break;
 		}
-		if (IS_ENABLED(CONFIG_RETPOLINE))
-			goto retpoline_auto;
+
+		mode = spectre_v2_select_retpoline();
 		break;
-	case SPECTRE_V2_CMD_RETPOLINE_AMD:
-		if (IS_ENABLED(CONFIG_RETPOLINE))
-			goto retpoline_amd;
+
+	case SPECTRE_V2_CMD_RETPOLINE_LFENCE:
+		pr_err(SPECTRE_V2_LFENCE_MSG);
+		mode = SPECTRE_V2_LFENCE;
 		break;
+
 	case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
-		if (IS_ENABLED(CONFIG_RETPOLINE))
-			goto retpoline_generic;
+		mode = SPECTRE_V2_RETPOLINE;
 		break;
+
 	case SPECTRE_V2_CMD_RETPOLINE:
-		if (IS_ENABLED(CONFIG_RETPOLINE))
-			goto retpoline_auto;
+		mode = spectre_v2_select_retpoline();
+		break;
+
+	case SPECTRE_V2_CMD_EIBRS:
+		mode = SPECTRE_V2_EIBRS;
+		break;
+
+	case SPECTRE_V2_CMD_EIBRS_LFENCE:
+		mode = SPECTRE_V2_EIBRS_LFENCE;
+		break;
+
+	case SPECTRE_V2_CMD_EIBRS_RETPOLINE:
+		mode = SPECTRE_V2_EIBRS_RETPOLINE;
 		break;
 	}
-	pr_err("Spectre mitigation: kernel not compiled with retpoline; no mitigation available!");
-	return;
 
-retpoline_auto:
-	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
-	    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
-	retpoline_amd:
-		if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
-			pr_err("Spectre mitigation: LFENCE not serializing, switching to generic retpoline\n");
-			goto retpoline_generic;
+	if (mode == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())
+		pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
+
+	if (spectre_v2_in_eibrs_mode(mode)) {
+		/* Force it so VMEXIT will restore correctly */
+		x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
+		wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 	}
-		mode = SPECTRE_V2_RETPOLINE_AMD;
-		setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
-		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
-	} else {
-	retpoline_generic:
-		mode = SPECTRE_V2_RETPOLINE_GENERIC;
+
+	switch (mode) {
+	case SPECTRE_V2_NONE:
+	case SPECTRE_V2_EIBRS:
+		break;
+
+	case SPECTRE_V2_LFENCE:
+	case SPECTRE_V2_EIBRS_LFENCE:
+		setup_force_cpu_cap(X86_FEATURE_RETPOLINE_LFENCE);
+		fallthrough;
+
+	case SPECTRE_V2_RETPOLINE:
+	case SPECTRE_V2_EIBRS_RETPOLINE:
 		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
+		break;
 	}
 
-specv2_set_mode:
 	spectre_v2_enabled = mode;
 	pr_info("%s\n", spectre_v2_strings[mode]);
 
@@ -975,7 +1063,7 @@ static void __init spectre_v2_select_mitigation(void)
 	 * the CPU supports Enhanced IBRS, kernel might un-intentionally not
 	 * enable IBRS around firmware calls.
 	 */
-	if (boot_cpu_has(X86_FEATURE_IBRS) && mode != SPECTRE_V2_IBRS_ENHANCED) {
+	if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_eibrs_mode(mode)) {
 		setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW);
 		pr_info("Enabling Restricted Speculation for firmware calls\n");
 	}
@@ -1045,6 +1133,10 @@ void cpu_bugs_smt_update(void)
 {
 	mutex_lock(&spec_ctrl_mutex);
 
+	if (sched_smt_active() && unprivileged_ebpf_enabled() &&
+	    spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
+		pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
+
 	switch (spectre_v2_user_stibp) {
 	case SPECTRE_V2_USER_NONE:
 		break;
@@ -1684,7 +1776,7 @@ static ssize_t tsx_async_abort_show_state(char *buf)
 
 static char *stibp_state(void)
 {
-	if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+	if (spectre_v2_in_eibrs_mode(spectre_v2_enabled))
 		return "";
 
 	switch (spectre_v2_user_stibp) {
@@ -1714,6 +1806,27 @@ static char *ibpb_state(void)
 	return "";
 }
 
+static ssize_t spectre_v2_show_state(char *buf)
+{
+	if (spectre_v2_enabled == SPECTRE_V2_LFENCE)
+		return sprintf(buf, "Vulnerable: LFENCE\n");
+
+	if (spectre_v2_enabled == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())
+		return sprintf(buf, "Vulnerable: eIBRS with unprivileged eBPF\n");
+
+	if (sched_smt_active() && unprivileged_ebpf_enabled() &&
+	    spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
+		return sprintf(buf, "Vulnerable: eIBRS+LFENCE with unprivileged eBPF and SMT\n");
+
+	return sprintf(buf, "%s%s%s%s%s%s\n",
+		       spectre_v2_strings[spectre_v2_enabled],
+		       ibpb_state(),
+		       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
+		       stibp_state(),
+		       boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",
+		       spectre_v2_module_string());
+}
+
 static ssize_t srbds_show_state(char *buf)
 {
 	return sprintf(buf, "%s\n", srbds_strings[srbds_mitigation]);
@@ -1739,12 +1852,7 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
 		return sprintf(buf, "%s\n", spectre_v1_strings[spectre_v1_mitigation]);
 
 	case X86_BUG_SPECTRE_V2:
-		return sprintf(buf, "%s%s%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
-			       ibpb_state(),
-			       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
-			       stibp_state(),
-			       boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",
-			       spectre_v2_module_string());
+		return spectre_v2_show_state(buf);
 
 	case X86_BUG_SPEC_STORE_BYPASS:
 		return sprintf(buf, "%s\n", ssb_strings[ssb_mode]);

arch/x86/lib/retpoline.S

@@ -34,7 +34,7 @@ SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL)
 
 	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
 		      __stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \
-		      __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg; int3), X86_FEATURE_RETPOLINE_AMD
+		      __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg; int3), X86_FEATURE_RETPOLINE_LFENCE
 
 .endm
 

arch/x86/net/bpf_jit_comp.c

@@ -394,7 +394,7 @@ static void emit_indirect_jump(u8 **pprog, int reg, u8 *ip)
 	u8 *prog = *pprog;
 
 #ifdef CONFIG_RETPOLINE
-	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_AMD)) {
+	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) {
 		EMIT_LFENCE();
 		EMIT2(0xFF, 0xE0 + reg);
 	} else if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) {

include/linux/bpf.h

@@ -1792,6 +1792,11 @@ struct bpf_core_ctx {
 int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
 		   int relo_idx, void *insn);
 
+static inline bool unprivileged_ebpf_enabled(void)
+{
+	return !sysctl_unprivileged_bpf_disabled;
+}
+
 #else /* !CONFIG_BPF_SYSCALL */
 static inline struct bpf_prog *bpf_prog_get(u32 ufd)
 {
@@ -2011,6 +2016,12 @@ bpf_jit_find_kfunc_model(const struct bpf_prog *prog,
 {
 	return NULL;
 }
+
+static inline bool unprivileged_ebpf_enabled(void)
+{
+	return false;
+}
+
 #endif /* CONFIG_BPF_SYSCALL */
 
 void __bpf_free_used_btfs(struct bpf_prog_aux *aux,

kernel/sysctl.c

@@ -180,6 +180,10 @@ static int bpf_stats_handler(struct ctl_table *table, int write,
 	return ret;
 }
 
+void __weak unpriv_ebpf_notify(int new_state)
+{
+}
+
 static int bpf_unpriv_handler(struct ctl_table *table, int write,
 			      void *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -197,6 +201,9 @@ static int bpf_unpriv_handler(struct ctl_table *table, int write,
 			return -EPERM;
 		*(int *)table->data = unpriv_enable;
 	}
+
+	unpriv_ebpf_notify(unpriv_enable);
+
 	return ret;
 }
 #endif /* CONFIG_BPF_SYSCALL && CONFIG_SYSCTL */

tools/arch/x86/include/asm/cpufeatures.h

@@ -204,7 +204,7 @@
 /* FREE!                                ( 7*32+10) */
 #define X86_FEATURE_PTI			( 7*32+11) /* Kernel Page Table Isolation enabled */
 #define X86_FEATURE_RETPOLINE		( 7*32+12) /* "" Generic Retpoline mitigation for Spectre variant 2 */
-#define X86_FEATURE_RETPOLINE_AMD	( 7*32+13) /* "" AMD Retpoline mitigation for Spectre variant 2 */
+#define X86_FEATURE_RETPOLINE_LFENCE	( 7*32+13) /* "" Use LFENCEs for Spectre variant 2 */
 #define X86_FEATURE_INTEL_PPIN		( 7*32+14) /* Intel Processor Inventory Number */
 #define X86_FEATURE_CDP_L2		( 7*32+15) /* Code and Data Prioritization L2 */
 #define X86_FEATURE_MSR_SPEC_CTRL	( 7*32+16) /* "" MSR SPEC_CTRL is implemented */