[RFC PATCH 16/39] KVM: guest_memfd: Add page alignment check for hugetlb guest_memfd

[Ackerley Tng]

When a hugetlb guest_memfd is requested, the requested size should be
aligned to the size of the hugetlb page requested.

Signed-off-by: Ackerley Tng <ackerley...@google.com>
---
 virt/kvm/guest_memfd.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 2e6f12e2bac8..eacbfdb950d1 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -909,6 +909,13 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, 
u64 flags)
        return err;
 }
 
+static inline bool kvm_gmem_hugetlb_page_aligned(u32 flags, u64 value)
+{
+       int page_size_log = (flags >> KVM_GUEST_MEMFD_HUGE_SHIFT) & 
KVM_GUEST_MEMFD_HUGE_MASK;
+       u64 page_size = 1ULL << page_size_log;
+       return IS_ALIGNED(value, page_size);
+}
+
 #define KVM_GUEST_MEMFD_ALL_FLAGS KVM_GUEST_MEMFD_HUGETLB
 
 int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args)
@@ -921,12 +928,18 @@ int kvm_gmem_create(struct kvm *kvm, struct 
kvm_create_guest_memfd *args)
                if (flags & ~(KVM_GUEST_MEMFD_ALL_FLAGS |
                              (KVM_GUEST_MEMFD_HUGE_MASK << 
KVM_GUEST_MEMFD_HUGE_SHIFT)))
                        return -EINVAL;
+
+               if (!kvm_gmem_hugetlb_page_aligned(flags, size))
+                       return -EINVAL;
        } else {
                if (flags & ~KVM_GUEST_MEMFD_ALL_FLAGS)
                        return -EINVAL;
+
+               if (!PAGE_ALIGNED(size))
+                       return -EINVAL;
        }
 
-       if (size <= 0 || !PAGE_ALIGNED(size))
+       if (size <= 0)
                return -EINVAL;
 
        return __kvm_gmem_create(kvm, size, flags);
-- 
2.46.0.598.g6f2099f65c-goog