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| author | Sean Christopherson <seanjc@google.com> | 2026-05-01 13:22:35 -0700 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2026-05-29 20:25:29 +0200 |
| commit | c8cc238093ca6c99267032f6cfe78f59389f3157 (patch) | |
| tree | ae7749e898b104245f073e2c16b4f7272fb04839 /arch | |
| parent | 121d88de56bc5c0ba0ce2f6381af67f948a7e7c1 (diff) | |
| download | linux-next-c8cc238093ca6c99267032f6cfe78f59389f3157.tar.gz linux-next-c8cc238093ca6c99267032f6cfe78f59389f3157.zip | |
KVM: SEV: Use READ_ONCE() when reading entries/indices from PSC buffer
Use READ_ONCE() when reading entries/indices from the guest-accessible
Page State Change buffer to defend against TOCTOU bugs.
Don't bother with READ_ONCE()/WRITE_ONCE() for cases where KVM is writing
(and not consuming the result!), as the guest isn't supposed to touch the
buffer while it's being processed. I.e. using READ_ONCE() is all about
protecting against misbehaving guests.
Fixes: 9b54e248d264 ("KVM: SEV: Add support to handle Page State Change VMGEXIT")
Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/svm/sev.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 6e8cbae2135a..62b5befe0eed 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -3872,9 +3872,9 @@ static void __snp_complete_one_psc(struct vcpu_svm *svm) */ for (idx = svm->sev_es.psc_idx; svm->sev_es.psc_inflight; svm->sev_es.psc_inflight--, idx++) { - struct psc_entry *entry = &entries[idx]; + struct psc_entry entry = READ_ONCE(entries[idx]); - entry->cur_page = entry->pagesize ? 512 : 1; + entries[idx].cur_page = entry.pagesize ? 512 : 1; } hdr->cur_entry = idx; @@ -3938,8 +3938,8 @@ next_range: * validation, so take care to only use validated copies of values used * for things like array indexing. */ - idx_start = hdr->cur_entry; - idx_end = hdr->end_entry; + idx_start = READ_ONCE(hdr->cur_entry); + idx_end = READ_ONCE(hdr->end_entry); if (idx_end >= max_nr_entries) { snp_complete_psc(svm, VMGEXIT_PSC_ERROR_INVALID_HDR); @@ -3948,7 +3948,7 @@ next_range: /* Find the start of the next range which needs processing. */ for (idx = idx_start; idx <= idx_end; idx++, hdr->cur_entry++) { - entry_start = entries[idx]; + entry_start = READ_ONCE(entries[idx]); gfn = entry_start.gfn; huge = entry_start.pagesize; @@ -3992,7 +3992,7 @@ next_range: * KVM_HC_MAP_GPA_RANGE exit. */ while (++idx <= idx_end) { - struct psc_entry entry = entries[idx]; + struct psc_entry entry = READ_ONCE(entries[idx]); if (entry.operation != entry_start.operation || entry.gfn != entry_start.gfn + npages || |