The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6b285a5587506bae084cf9a3ed5aa491d623b91b Mon Sep 17 00:00:00 2001

From: Sean Christopherson seanjc@google.com Date: Thu, 4 Nov 2021 00:25:03 +0000 Subject: [PATCH] KVM: Disallow user memslot with size that exceeds "unsigned long"

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 Reviewed-by: Maciej S. Szmigiero maciej.szmigiero@oracle.com Message-Id: 20211104002531.1176691-3-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 2104fc29cdd2..6c5083f2eb50 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;