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| author | Sean Christopherson <seanjc@google.com> | 2024-08-29 12:14:13 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2024-09-09 20:15:34 -0700 |
| commit | 025dde582bbf31e7618f9283594ef5e2408e384b (patch) | |
| tree | d722a6ec8fd040e4029ec6b43336d31131b88799 /virt/kvm | |
| parent | ec495f2ab12290b008a691e826b39b895f458945 (diff) | |
| download | lwn-025dde582bbf31e7618f9283594ef5e2408e384b.tar.gz lwn-025dde582bbf31e7618f9283594ef5e2408e384b.zip | |
KVM: Harden guest memory APIs against out-of-bounds accesses
When reading or writing a guest page, WARN and bail if offset+len would
result in a read to a different page so that KVM bugs are more likely to
be detected, and so that any such bugs are less likely to escalate to an
out-of-bounds access. E.g. if userspace isn't using guard pages and the
target page is at the end of a memslot.
Note, KVM already hardens itself in similar APIs, e.g. in the "cached"
variants, it's just the vanilla APIs that are playing with fire.
Link: https://lore.kernel.org/r/20240829191413.900740-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'virt/kvm')
| -rw-r--r-- | virt/kvm/kvm_main.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 04011b94edec..d51357fd28d7 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3275,6 +3275,9 @@ static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn, int r; unsigned long addr; + if (WARN_ON_ONCE(offset + len > PAGE_SIZE)) + return -EFAULT; + addr = gfn_to_hva_memslot_prot(slot, gfn, NULL); if (kvm_is_error_hva(addr)) return -EFAULT; @@ -3348,6 +3351,9 @@ static int __kvm_read_guest_atomic(struct kvm_memory_slot *slot, gfn_t gfn, int r; unsigned long addr; + if (WARN_ON_ONCE(offset + len > PAGE_SIZE)) + return -EFAULT; + addr = gfn_to_hva_memslot_prot(slot, gfn, NULL); if (kvm_is_error_hva(addr)) return -EFAULT; @@ -3378,6 +3384,9 @@ static int __kvm_write_guest_page(struct kvm *kvm, int r; unsigned long addr; + if (WARN_ON_ONCE(offset + len > PAGE_SIZE)) + return -EFAULT; + addr = gfn_to_hva_memslot(memslot, gfn); if (kvm_is_error_hva(addr)) return -EFAULT; |