From 025dde582bbf31e7618f9283594ef5e2408e384b Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 29 Aug 2024 12:14:13 -0700 Subject: 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 --- virt/kvm/kvm_main.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'virt') 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; -- cgit v1.2.3-70-g09d2