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AJvYcCW9+zOWncMayKY7c+cTHQnqitQj1Yj08US0FsOtHPiz+QrKuP6V9e4Yw+e6WtT+bd33cFzBTqoloFFCALWh@vger.kernel.org X-Gm-Message-State: AOJu0YzBvjMxYcGvlb2X2PMIGuWrmrz9GrBRdD22IfuNe3F3t7EU8x/R GhgWqRo8kp6Q1inlwSVX+vu+7MXnKKx/JkUgGIqDpkM0Ke1F6sSurxJJOJO4roqFhiJ1i3dbgw= = X-Google-Smtp-Source: AGHT+IHPBFphMwR0/rLp+gySy0dxBabpKT4zkEgWC/5U+nwhKCMIpmmhaC+Hj2shZb3rzwt63hBboV4t6w== X-Received: from wmbep21.prod.google.com ([2002:a05:600c:8415:b0:440:5e01:286b]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:37cd:b0:43c:e6d1:efe7 with SMTP id 5b1f17b1804b1-442d6dd21e9mr126542875e9.26.1747154097178; Tue, 13 May 2025 09:34:57 -0700 (PDT) Date: Tue, 13 May 2025 17:34:29 +0100 In-Reply-To: <20250513163438.3942405-1-tabba@google.com> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250513163438.3942405-1-tabba@google.com> X-Mailer: git-send-email 2.49.0.1045.g170613ef41-goog Message-ID: <20250513163438.3942405-9-tabba@google.com> Subject: [PATCH v9 08/17] KVM: guest_memfd: Check that userspace_addr and fd+offset refer to same range From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com, tabba@google.com From: Ackerley Tng On binding of a guest_memfd with a memslot, check that the slot's userspace_addr and the requested fd and offset refer to the same memory range. This check is best-effort: nothing prevents userspace from later mapping other memory to the same provided in slot->userspace_addr and breaking guest operation. Suggested-by: David Hildenbrand Suggested-by: Sean Christopherson Suggested-by: Yan Zhao Signed-off-by: Ackerley Tng Signed-off-by: Fuad Tabba --- virt/kvm/guest_memfd.c | 37 ++++++++++++++++++++++++++++++++++--- 1 file changed, 34 insertions(+), 3 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 8e6d1866b55e..2f499021df66 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -556,6 +556,32 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) return __kvm_gmem_create(kvm, size, flags); } +static bool kvm_gmem_is_same_range(struct kvm *kvm, + struct kvm_memory_slot *slot, + struct file *file, loff_t offset) +{ + struct mm_struct *mm = kvm->mm; + loff_t userspace_addr_offset; + struct vm_area_struct *vma; + bool ret = false; + + mmap_read_lock(mm); + + vma = vma_lookup(mm, slot->userspace_addr); + if (!vma) + goto out; + + if (vma->vm_file != file) + goto out; + + userspace_addr_offset = slot->userspace_addr - vma->vm_start; + ret = userspace_addr_offset + (vma->vm_pgoff << PAGE_SHIFT) == offset; +out: + mmap_read_unlock(mm); + + return ret; +} + int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned int fd, loff_t offset) { @@ -585,9 +611,14 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, offset + size > i_size_read(inode)) goto err; - if (kvm_gmem_supports_shared(inode) && - !kvm_arch_vm_supports_gmem_shared_mem(kvm)) - goto err; + if (kvm_gmem_supports_shared(inode)) { + if (!kvm_arch_vm_supports_gmem_shared_mem(kvm)) + goto err; + + if (slot->userspace_addr && + !kvm_gmem_is_same_range(kvm, slot, file, offset)) + goto err; + } filemap_invalidate_lock(inode->i_mapping);