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| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2024-04-10 22:40:48 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2024-04-11 10:30:33 +0200 |
| commit | 5f882f3b0a8bf0788d5a0ee44b1191de5319bb8a (patch) | |
| tree | e81864ff7a59b1a389fd57280ddbcc0ddf2f3c84 | |
| parent | 1cea8a280dfd1016148a3820676f2f03e3f5b898 (diff) | |
| download | linux-5f882f3b0a8bf0788d5a0ee44b1191de5319bb8a.tar.gz | |
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.rst | 11 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 6 |
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 3cf18e4a1d9ab2..5a39acf824835d 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 a029ad6c4963c3..a3874cc97892d9 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 08dfb94fcb3a41..9eeb60f5fbb356 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) |