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| author | Xiaoyao Li <xiaoyao.li@intel.com> | 2020-04-10 13:54:01 +0200 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2020-04-11 16:40:55 +0200 |
| commit | 9de6fe3c28d6d8feadfad907961f1f31b85c6985 (patch) | |
| tree | 7f2d97a3a8e88b134b5309f72275c092fb454c2d /arch | |
| parent | d7e94dbdac1a40924626b0efc7ff530c8baf5e4a (diff) | |
| download | linux-9de6fe3c28d6d8feadfad907961f1f31b85c6985.tar.gz | |
KVM: x86: Emulate split-lock access as a write in emulator
Emulate split-lock accesses as writes if split lock detection is on to avoid #AC during emulation, which will result in a panic(). This should never occur for a well-behaved guest, but a malicious guest can manipulate the TLB to trigger emulation of a locked instruction[1]. More discussion can be found at [2][3]. [1] https://lkml.kernel.org/r/8c5b11c9-58df-38e7-a514-dc12d687b198@redhat.com [2] https://lkml.kernel.org/r/20200131200134.GD18946@linux.intel.com [3] https://lkml.kernel.org/r/20200227001117.GX9940@linux.intel.com Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Link: https://lkml.kernel.org/r/20200410115517.084300242@linutronix.de
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/x86.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 027dfd278a97..3bf2ecafd027 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5839,6 +5839,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, { struct kvm_host_map map; struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); + u64 page_line_mask; gpa_t gpa; char *kaddr; bool exchanged; @@ -5853,7 +5854,16 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, (gpa & PAGE_MASK) == APIC_DEFAULT_PHYS_BASE) goto emul_write; - if (((gpa + bytes - 1) & PAGE_MASK) != (gpa & PAGE_MASK)) + /* + * Emulate the atomic as a straight write to avoid #AC if SLD is + * enabled in the host and the access splits a cache line. + */ + if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) + page_line_mask = ~(cache_line_size() - 1); + else + page_line_mask = PAGE_MASK; + + if (((gpa + bytes - 1) & page_line_mask) != (gpa & page_line_mask)) goto emul_write; if (kvm_vcpu_map(vcpu, gpa_to_gfn(gpa), &map)) |