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authorJosh Poimboeuf <jpoimboe@kernel.org>2024-04-11 07:40:48 +0200
committerIngo Molnar <mingo@kernel.org>2024-04-11 10:30:33 +0200
commit5f882f3b0a8bf0788d5a0ee44b1191de5319bb8a (patch)
treee81864ff7a59b1a389fd57280ddbcc0ddf2f3c84
parentx86/bugs: Fix BHI handling of RRSBA (diff)
downloadlinux-5f882f3b0a8bf0788d5a0ee44b1191de5319bb8a.tar.xz
linux-5f882f3b0a8bf0788d5a0ee44b1191de5319bb8a.zip
x86/bugs: Clarify that syscall hardening isn't a BHI mitigation
While syscall hardening helps prevent some BHI attacks, there's still other low-hanging fruit remaining. Don't classify it as a mitigation and make it clear that the system may still be vulnerable if it doesn't have a HW or SW mitigation enabled. Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/r/b5951dae3fdee7f1520d5136a27be3bdfe95f88b.1712813475.git.jpoimboe@kernel.org
-rw-r--r--Documentation/admin-guide/hw-vuln/spectre.rst11
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt3
-rw-r--r--arch/x86/kernel/cpu/bugs.c6
3 files changed, 9 insertions, 11 deletions
diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst
index 3cf18e4a1d9a..5a39acf82483 100644
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -441,10 +441,10 @@ The possible values in this file are:
- System is protected by BHI_DIS_S
* - BHI: SW loop, KVM SW loop
- System is protected by software clearing sequence
- * - BHI: Syscall hardening
- - Syscalls are hardened against BHI
- * - BHI: Syscall hardening, KVM: SW loop
- - System is protected from userspace attacks by syscall hardening; KVM is protected by software clearing sequence
+ * - BHI: Vulnerable
+ - System is vulnerable to BHI
+ * - BHI: Vulnerable, KVM: SW loop
+ - System is vulnerable; KVM is protected by software clearing sequence
Full mitigation might require a microcode update from the CPU
vendor. When the necessary microcode is not available, the kernel will
@@ -661,8 +661,7 @@ kernel command line.
spectre_bhi=
[X86] Control mitigation of Branch History Injection
- (BHI) vulnerability. Syscalls are hardened against BHI
- regardless of this setting. This setting affects the deployment
+ (BHI) vulnerability. This setting affects the deployment
of the HW BHI control and the SW BHB clearing sequence.
on
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a029ad6c4963..a3874cc97892 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6065,8 +6065,7 @@
See Documentation/admin-guide/laptops/sonypi.rst
spectre_bhi= [X86] Control mitigation of Branch History Injection
- (BHI) vulnerability. Syscalls are hardened against BHI
- reglardless of this setting. This setting affects the
+ (BHI) vulnerability. This setting affects the
deployment of the HW BHI control and the SW BHB
clearing sequence.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 08dfb94fcb3a..9eeb60f5fbb3 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2818,10 +2818,10 @@ static const char *spectre_bhi_state(void)
return "; BHI: SW loop, KVM: SW loop";
else if (boot_cpu_has(X86_FEATURE_RETPOLINE) && rrsba_disabled)
return "; BHI: Retpoline";
- else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT))
- return "; BHI: Syscall hardening, KVM: SW loop";
+ else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT))
+ return "; BHI: Vulnerable, KVM: SW loop";
- return "; BHI: Vulnerable (Syscall hardening enabled)";
+ return "; BHI: Vulnerable";
}
static ssize_t spectre_v2_show_state(char *buf)