Re: [PATCH v12 01/84] KVM: arm64: Release pfn, i.e. put page, if copying MTE tags hits ZONE_DEVICE
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2024-08-07 14:15:38
Also in:
kvm, kvm-riscv, kvmarm, linux-arm-kernel, linux-mips, linux-riscv, lkml, loongarch
On Fri, Jul 26, 2024 at 04:51:10PM -0700, Sean Christopherson wrote:
quoted hunk ↗ jump to hunk
Put the page reference acquired by gfn_to_pfn_prot() if kvm_vm_ioctl_mte_copy_tags() runs into ZONE_DEVICE memory. KVM's less- than-stellar heuristics for dealing with pfn-mapped memory means that KVM can get a page reference to ZONE_DEVICE memory. Fixes: f0376edb1ddc ("KVM: arm64: Add ioctl to fetch/store tags in a guest") Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/arm64/kvm/guest.c | 1 + 1 file changed, 1 insertion(+)diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c index 11098eb7eb44..e1f0ff08836a 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c@@ -1059,6 +1059,7 @@ int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, page = pfn_to_online_page(pfn); if (!page) { /* Reject ZONE_DEVICE memory */ + kvm_release_pfn_clean(pfn); ret = -EFAULT; goto out; }
This patch makes sense irrespective of whether the above pfn is a ZONE_DEVICE or not. gfn_to_pfn_prot() increased the page refcount via GUP, so it must be released before bailing out of this loop. Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>