[PATCH] Fix unsynchronized access to sev members through svm_register_enc_region
From: Peter Gonda <hidden>
Date: 2021-01-27 01:51:46
Also in:
kvm, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
sev_pin_memory assumes that callers hold the kvm->lock. This was true for all callers except svm_register_enc_region since it does not originate from svm_mem_enc_op. Also added lockdep annotation to help prevent future regressions. Tested: Booted SEV enabled VM on host. Cc: Thomas Gleixner <redacted> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Brijesh Singh <redacted> Cc: Sean Christopherson <seanjc@google.com> Cc: x86@kernel.org Cc: kvm@vger.kernel.org Cc: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org Fixes: 116a2214c5173 (KVM: SVM: Pin guest memory when SEV is active) Signed-off-by: Peter Gonda <redacted> --- arch/x86/kvm/svm.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index afdc5b44fe9f..9884e57f3d0f 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c@@ -1699,6 +1699,8 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr, struct page **pages; unsigned long first, last; + lockdep_assert_held(&kvm->lock); + if (ulen == 0 || uaddr + ulen < uaddr) return NULL;
@@ -7228,12 +7230,19 @@ static int svm_register_enc_region(struct kvm *kvm, if (!region) return -ENOMEM; + mutex_lock(&kvm->lock); region->pages = sev_pin_memory(kvm, range->addr, range->size, ®ion->npages, 1); if (!region->pages) { ret = -ENOMEM; goto e_free; } + region->uaddr = range->addr; + region->size = range->size; + + list_add_tail(®ion->list, &sev->regions_list); + mutex_unlock(&kvm->lock); + /* * The guest may change the memory encryption attribute from C=0 -> C=1 * or vice versa for this memory range. Lets make sure caches are
@@ -7242,13 +7251,6 @@ static int svm_register_enc_region(struct kvm *kvm, */ sev_clflush_pages(region->pages, region->npages); - region->uaddr = range->addr; - region->size = range->size; - - mutex_lock(&kvm->lock); - list_add_tail(®ion->list, &sev->regions_list); - mutex_unlock(&kvm->lock); - return ret; e_free:
--
2.30.0.280.ga3ce27912f-goog