From: Zongyao Chen KVM_SET_USER_MEMORY_REGION2 rejects guest_memfd ranges that overlap an existing binding, but kvm_gmem_bind() currently reports the failure through its generic -EINVAL path. That makes binding conflicts indistinguishable from malformed guest_memfd parameters. Return -EEXIST when the target guest_memfd range is already bound, matching the errno used for overlapping GPA memslots and making the two types of range conflicts report the same class of error to userspace. Note, returning -EINVAL was definitely not intentional, as guest_memfd support was accompanied by a selftest to verify that attempting to create overlapping bindings fails with -EEXIST. Except the selftest was also flawed in that it unintentionally overlapped memslot GPAs, and so failed on KVM's common memslot checks before reaching guest_memfd. Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory") Signed-off-by: Zongyao Chen Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng [sean: call out that the original intent was to return -EEXIST] Signed-off-by: Sean Christopherson --- virt/kvm/guest_memfd.c | 1 + 1 file changed, 1 insertion(+) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 69c9d6d546b2..46727539d08a 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -675,6 +675,7 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, if (!xa_empty(&f->bindings) && xa_find(&f->bindings, &start, end - 1, XA_PRESENT)) { + r = -EEXIST; filemap_invalidate_unlock(inode->i_mapping); goto err; } -- 2.54.0.794.g4f17f83d09-goog