diff options
| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2024-04-10 22:40:48 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-04-17 11:15:17 +0200 |
| commit | ebba2270ab744bd9eb8927ff1624f64cb3fe4ca4 (patch) | |
| tree | 0d4aba076d2a88d3a0df1fa535af44cd4cf25373 | |
| parent | e47d1cbde75936be6538c05737c88292b9d9c31d (diff) | |
x86/bugs: Clarify that syscall hardening isn't a BHI mitigation
commit 5f882f3b0a8bf0788d5a0ee44b1191de5319bb8a upstream.
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 06b27317638a..22492b75ff42 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 @@ -711,8 +711,7 @@ For user space mitigation: 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 0c63b64304c9..2ff2e5056c97 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5406,8 +5406,7 @@ 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 0a40b4a7de2c..dafb854603f0 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -2797,10 +2797,10 @@ 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) |