[v6] Attack vector controls (part 2)

[PATCH v6 17/21] x86/bugs: Add attack vector controls for SRSO

Posted by David Kaplan 2 months, 4 weeks ago

Use attack vector controls to determine if SRSO mitigation is required.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
---
 arch/x86/kernel/cpu/bugs.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index ecfd7d728ac5..c0e23e625b6f 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -3012,14 +3012,19 @@ early_param("spec_rstack_overflow", srso_parse_cmdline);
 
 static void __init srso_select_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
+	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
 		srso_mitigation = SRSO_MITIGATION_NONE;
-
-	if (srso_mitigation == SRSO_MITIGATION_NONE)
 		return;
+	}
 
-	if (srso_mitigation == SRSO_MITIGATION_AUTO)
-		srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+	if (srso_mitigation == SRSO_MITIGATION_AUTO) {
+		if (should_mitigate_vuln(X86_BUG_SRSO)) {
+			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+		} else {
+			srso_mitigation = SRSO_MITIGATION_NONE;
+			return;
+		}
+	}
 
 	/* Zen1/2 with SMT off aren't vulnerable to SRSO. */
 	if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {
-- 
2.34.1

[tip: x86/bugs] x86/bugs: Add attack vector controls for SRSO

Posted by tip-bot2 for David Kaplan 2 months, 3 weeks ago

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     eda718fde6159b2e64978637ebb3f1ae98180555
Gitweb:        https://git.kernel.org/tip/eda718fde6159b2e64978637ebb3f1ae98180555
Author:        David Kaplan <david.kaplan@amd.com>
AuthorDate:    Mon, 07 Jul 2025 13:33:12 -05:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 11 Jul 2025 17:56:41 +02:00

x86/bugs: Add attack vector controls for SRSO

Use attack vector controls to determine if SRSO mitigation is required.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250707183316.1349127-18-david.kaplan@amd.com
---
 arch/x86/kernel/cpu/bugs.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 2128623..eef6ccd 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -3123,14 +3123,19 @@ early_param("spec_rstack_overflow", srso_parse_cmdline);
 
 static void __init srso_select_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
+	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
 		srso_mitigation = SRSO_MITIGATION_NONE;
-
-	if (srso_mitigation == SRSO_MITIGATION_NONE)
 		return;
+	}
 
-	if (srso_mitigation == SRSO_MITIGATION_AUTO)
-		srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+	if (srso_mitigation == SRSO_MITIGATION_AUTO) {
+		if (should_mitigate_vuln(X86_BUG_SRSO)) {
+			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+		} else {
+			srso_mitigation = SRSO_MITIGATION_NONE;
+			return;
+		}
+	}
 
 	/* Zen1/2 with SMT off aren't vulnerable to SRSO. */
 	if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {