| Message ID | 20211104002531.1176691-3-seanjc@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: Scalable memslots implementation | expand |
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>
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;
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(-)