From: Sean Christopherson <seanjc@google.com> stable inclusion from stable-v5.10.229 commit 76ce386feb14ec9a460784fcd495d8432acce7a5 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IB2BXL CVE: CVE-2024-50115 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit f559b2e9c5c5308850544ab59396b7d53cfc67bd upstream. Ignore nCR3[4:0] when loading PDPTEs from memory for nested SVM, as bits 4:0 of CR3 are ignored when PAE paging is used, and thus VMRUN doesn't enforce 32-byte alignment of nCR3. In the absolute worst case scenario, failure to ignore bits 4:0 can result in an out-of-bounds read, e.g. if the target page is at the end of a memslot, and the VMM isn't using guard pages. Per the APM: The CR3 register points to the base address of the page-directory-pointer table. The page-directory-pointer table is aligned on a 32-byte boundary, with the low 5 address bits 4:0 assumed to be 0. And the SDM's much more explicit: 4:0 Ignored Note, KVM gets this right when loading PDPTRs, it's only the nSVM flow that is broken. Fixes: e4e517b4be01 ("KVM: MMU: Do not unconditionally read PDPTE from guest memory") Reported-by: Kirk Swidowski <swidowski@google.com> Cc: Andy Nguyen <theflow@google.com> Cc: 3pvd <3pvd@google.com> Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Message-ID: <20241009140838.1036226-1-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Liao Chen <liaochen4@huawei.com> --- arch/x86/kvm/svm/nested.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 0c164ca686c7..f62d373c2428 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -75,8 +75,12 @@ static u64 nested_svm_get_tdp_pdptr(struct kvm_vcpu *vcpu, int index) u64 pdpte; int ret; + /* + * Note, nCR3 is "assumed" to be 32-byte aligned, i.e. the CPU ignores + * nCR3[4:0] when loading PDPTEs from memory. + */ ret = kvm_vcpu_read_guest_page(vcpu, gpa_to_gfn(cr3), &pdpte, - offset_in_page(cr3) + index * 8, 8); + (cr3 & GENMASK(11, 5)) + index * 8, 8); if (ret) return 0; return pdpte; -- 2.34.1