| From | "Maciej S. Szmigiero" <> | Subject | Re: [PATCH v5.5 02/30] KVM: Disallow user memslot with size that exceeds "unsigned long" | Date | Tue, 9 Nov 2021 01:38:02 +0100 |
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On 04.11.2021 01:25, Sean Christopherson wrote: > Reject userspace memslots whose size exceeds the storage capacity of an > "unsigned long". KVM's uAPI takes the size as u64 to support large slots > on 64-bit hosts, but does not account for the size being truncated on > 32-bit hosts in various flows. The access_ok() check on the userspace > virtual address in particular casts the size to "unsigned long" and will > check the wrong number of bytes. > > KVM doesn't actually support slots whose size doesn't fit in an "unsigned > long", e.g. KVM's internal kvm_memory_slot.npages is an "unsigned long", > not a "u64", and misc arch specific code follows that behavior. > > Fixes: fa3d315a4ce2 ("KVM: Validate userspace_addr of memslot when registered") > Cc: stable@vger.kernel.org > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > virt/kvm/kvm_main.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 99e69375c4c9..83287730389f 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1689,7 +1689,8 @@ int __kvm_set_memory_region(struct kvm *kvm, > id = (u16)mem->slot; > > /* General sanity checks */ > - if (mem->memory_size & (PAGE_SIZE - 1)) > + if ((mem->memory_size & (PAGE_SIZE - 1)) || > + (mem->memory_size != (unsigned long)mem->memory_size)) > return -EINVAL; > if (mem->guest_phys_addr & (PAGE_SIZE - 1)) > return -EINVAL; >
Reviewed-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
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