From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Maciej S. Szmigiero" Date: Tue, 09 Nov 2021 00:38:02 +0000 Subject: Re: [PATCH v5.5 02/30] KVM: Disallow user memslot with size that exceeds "unsigned long" Message-Id: <2f451590-bf89-d447-d92a-fe9f3f41ca74@oracle.com> List-Id: References: <20211104002531.1176691-1-seanjc@google.com> <20211104002531.1176691-3-seanjc@google.com> In-Reply-To: <20211104002531.1176691-3-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Sean Christopherson Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Ben Gardon , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Paolo Bonzini 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 > --- > 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