diff options
| author |   David Kaplan <david.kaplan@amd.com> | 2025-07-21 11:03:10 -0500 |
|---|---|---|
| committer |   Borislav Petkov (AMD) <bp@alien8.de> | 2025-08-11 17:32:36 +0200 |
| commit | 4fa7d880aeb8cdbdaa4fb72be3e53ac1d6bcc088 (patch) | |
| tree | f5eba150c46c41f8bd0734cbc29232c01947b411 | |
| parent | Linux 6.17-rc1 (diff) | |
| download | wireguard-linux-4fa7d880aeb8cdbdaa4fb72be3e53ac1d6bcc088.tar.xz wireguard-linux-4fa7d880aeb8cdbdaa4fb72be3e53ac1d6bcc088.zip | |
x86/bugs: Select best SRSO mitigation
The SRSO bug can theoretically be used to conduct user->user or guest->guest
attacks and requires a mitigation (namely IBPB instead of SBPB on context
switch) for these. So mark SRSO as being applicable to the user->user and
guest->guest attack vectors.
Additionally, SRSO supports multiple mitigations which mitigate different
potential attack vectors. Some CPUs are also immune to SRSO from
certain attack vectors (like user->kernel).
Use the specific attack vectors requiring mitigation to select the best
SRSO mitigation to avoid unnecessary performance hits.
Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250721160310.1804203-1-david.kaplan@amd.com
| -rw-r--r-- | Documentation/admin-guide/hw-vuln/attack_vector_controls.rst | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 13 |
2 files changed, 12 insertions, 3 deletions
diff --git a/Documentation/admin-guide/hw-vuln/attack_vector_controls.rst b/Documentation/admin-guide/hw-vuln/attack_vector_controls.rst index b4de16f5ec44..6dd0800146f6 100644 --- a/Documentation/admin-guide/hw-vuln/attack_vector_controls.rst +++ b/Documentation/admin-guide/hw-vuln/attack_vector_controls.rst @@ -214,7 +214,7 @@ Spectre_v1 X Spectre_v2 X X Spectre_v2_user X X * (Note 1) SRBDS X X X X -SRSO X X +SRSO X X X X SSB (Note 4) TAA X X X X * (Note 2) TSA X X X X diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index b74bf937cd9f..2186a771b9fc 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -386,7 +386,6 @@ static bool __init should_mitigate_vuln(unsigned int bug) case X86_BUG_SPECTRE_V2: case X86_BUG_RETBLEED: - case X86_BUG_SRSO: case X86_BUG_L1TF: case X86_BUG_ITS: return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) || @@ -3184,8 +3183,18 @@ static void __init srso_select_mitigation(void) } if (srso_mitigation == SRSO_MITIGATION_AUTO) { - if (should_mitigate_vuln(X86_BUG_SRSO)) { + /* + * Use safe-RET if user->kernel or guest->host protection is + * required. Otherwise the 'microcode' mitigation is sufficient + * to protect the user->user and guest->guest vectors. + */ + if (cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) || + (cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) && + !boot_cpu_has(X86_FEATURE_SRSO_USER_KERNEL_NO))) { srso_mitigation = SRSO_MITIGATION_SAFE_RET; + } else if (cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) || + cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST)) { + srso_mitigation = SRSO_MITIGATION_MICROCODE; } else { srso_mitigation = SRSO_MITIGATION_NONE; return; |