In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
KVM: x86: Fix shadow paging use-after-free due to unexpected role<\/p>\n
Commit 0cb2af2ea66ad (“KVM: x86: Fix shadow paging use-after-free due
\nto unexpected GFN”) fixed a shadow paging mismatch between stored and
\ncomputed GFNs; the bug could be triggered by changing a PDE mapping from
\noutside the guest, and then deleting a memslot. The rmap_remove()
\ncall would miss entries created after the PDE change because the GFN
\nof the leaf SPTE does not match the GFN of the struct kvm_mmu_page.<\/p>\n
A similar hole however remains if the modified PDE points to a non-leaf
\npage. In this case the gfn can be made to match, but the role does not
\nmatch: the original large 2MB page creates a kvm_mmu_page with direct=1,
\nwhile the new 4KB needs a kvm_mmu_page with direct=0. However,
\nkvm_mmu_get_child_sp() does not compare the role, and therefore reuses
\nthe page.<\/p>\n
The next step is installing a leaf (4KB) SPTE on the new path which
\nrecords an rmap entry under the gfn resolved by the walk. But when
\nthat child is zapped its parent kvm_mmu_page has direct=1 and
\nkvm_mmu_page_get_gfn() computes the gfn for the 4KB page as
\nsp->gfn + index instead of using sp->shadowed_translation[] (or sp->gfns[]
\nin older kernels). It therefore fails to remove the recorded entry.<\/p>\n
When the memslot is dropped the shadow page is freed but the rmap
\nentry survives, as in the scenario that was already fixed. Code that
\nlater walks that gfn (dirty logging, MMU notifier invalidation, and
\nso on) dereferences an sptep that lies in the freed page, causing the
\nuse-after-free.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
KVM: x86: Fix shadow paging use-after-free due to unexpected role<\/p>\n
Commit 0cb2af2ea66ad (“KVM: x86: Fix shadow paging use-after-fre<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-12895","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/12895","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12895"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12895"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12895"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}