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x86/bugs: Define attack vectors relevant for each bug

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Add a function which defines which vulnerabilities should be mitigated
based on the selected attack vector controls.  The selections here are
based on the individual characteristics of each vulnerability.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250707183316.1349127-5-david.kaplan@amd.com
This commit is contained in:
David Kaplan 2025-07-07 13:32:59 -05:00 • committed by Borislav Petkov (AMD)
parent 735e59204b
commit 2d31d28746
1 changed files with 56 additions and 0 deletions
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56
arch/x86/kernel/cpu/bugs.c
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@ -332,6 +332,62 @@ static void x86_amd_ssb_disable(void)
#undef pr_fmt
#define pr_fmt(fmt) "MDS: " fmt
/*
* Returns true if vulnerability should be mitigated based on the
* selected attack vector controls.
*
* See Documentation/admin-guide/hw-vuln/attack_vector_controls.rst
*/
static bool __init should_mitigate_vuln(unsigned int bug)
{
switch (bug) {
/*
* The only runtime-selected spectre_v1 mitigations in the kernel are
* related to SWAPGS protection on kernel entry. Therefore, protection
* is only required for the user->kernel attack vector.
*/
case X86_BUG_SPECTRE_V1:
return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL);
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) ||
cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST);
case X86_BUG_SPECTRE_V2_USER:
return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) ||
cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST);
/*
* All the vulnerabilities below allow potentially leaking data
* across address spaces. Therefore, mitigation is required for
* any of these 4 attack vectors.
*/
case X86_BUG_MDS:
case X86_BUG_TAA:
case X86_BUG_MMIO_STALE_DATA:
case X86_BUG_RFDS:
case X86_BUG_SRBDS:
return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) ||
cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) ||
cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) ||
cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST);
case X86_BUG_GDS:
return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) ||
cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) ||
cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) ||
cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST) ||
(smt_mitigations != SMT_MITIGATIONS_OFF);
default:
WARN(1, "Unknown bug %x\n", bug);
return false;
}
}
/* Default mitigation for MDS-affected CPUs */
static enum mds_mitigations mds_mitigation __ro_after_init =
IS_ENABLED(CONFIG_MITIGATION_MDS) ? MDS_MITIGATION_AUTO : MDS_MITIGATION_OFF;