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Fri, 08 May 2026 00:58:28 -0700 (PDT) Received: from localhost.localdomain ([240e:47c:d8d0:4133:1cd2:48d8:fcfa:10ea]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-83967dbdfb0sm10998532b3a.45.2026.05.08.00.58.25 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 08 May 2026 00:58:28 -0700 (PDT) To: mst@redhat.com Cc: jasowang@redhat.com, w@1wt.eu, eperezma@redhat.com, Qihang Tang , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, virtualization@lists.linux.dev Subject: [PATCH v5] vhost/vdpa: validate virtqueue index in mmap and fault paths Date: Fri, 8 May 2026 15:58:21 +0800 Message-Id: <20260508075821.92656-1-q.h.hack.winter@gmail.com> In-Reply-To: <20260508063745.90506-1-q.h.hack.winter@gmail.com> References: <20260508063745.90506-1-q.h.hack.winter@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xYBbRmrejl6wZYb-1BK7Pc6jkCvbRJL8CEXZ3d2v8HM_1778227109 X-Mimecast-Impersonation-Protect: Policy=DMARC Check - CHG0118091;Similar Internal Domain=false;Similar Monitored External Domain=false;Custom External Domain=false;Mimecast External Domain=false;Newly Observed Domain=false;Internal User Name=false;Custom Display Name List=false;Reply-to Address Mismatch=false;Targeted Threat Dictionary=false;Mimecast Threat Dictionary=false;Custom Threat Dictionary=false X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition;Similar Internal Domain=false;Similar Monitored External Domain=false;Custom External Domain=false;Mimecast External Domain=false;Newly Observed Domain=false;Internal User Name=false;Custom Display Name List=false;Reply-to Address Mismatch=false;Targeted Threat Dictionary=false;Mimecast Threat Dictionary=false;Custom Threat Dictionary=false Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Label: todo vhost_vdpa_mmap() and vhost_vdpa_fault() use vma->vm_pgoff as a virtqueue index for get_vq_notification(), but they do not validate that the index is smaller than v->nvqs. The ioctl path already performs both a bounds check and array_index_nospec(), but the mmap/fault path only checks that the index fits in u16. This allows an out-of-range queue index to reach driver-specific get_vq_notification() callbacks. Fix this by extracting a unified vhost_vdpa_get_vq_notification() helper that validates the queue index against v->nvqs and applies array_index_nospec() before calling the driver callback. Both the mmap and fault paths use this helper, and the bounds checking is consolidated into a single location. >>From source inspection, the most defensible impact is out-of-bounds access in the callback path, potentially leading to invalid PFN remaps and crash/DoS. Fixes: ddd89d0a059d ("vhost_vdpa: support doorbell mapping via mmap") Acked-by: Eugenio Pérez Acked-by: Michael S. Tsirkin Signed-off-by: Qihang Tang --- drivers/vhost/vdpa.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index 692564b1bcbb..ac55275fa0d0 100644 --- a/drivers/vhost/vdpa.c +++ b/drivers/vhost/vdpa.c @@ -1482,16 +1482,32 @@ static int vhost_vdpa_release(struct inode *inode, struct file *filep) } #ifdef CONFIG_MMU -static vm_fault_t vhost_vdpa_fault(struct vm_fault *vmf) +static int +vhost_vdpa_get_vq_notification(struct vhost_vdpa *v, unsigned long index, + struct vdpa_notification_area *notify) { - struct vhost_vdpa *v = vmf->vma->vm_file->private_data; struct vdpa_device *vdpa = v->vdpa; const struct vdpa_config_ops *ops = vdpa->config; + + if (index > 65535 || index >= v->nvqs) + return -EINVAL; + + index = array_index_nospec(index, v->nvqs); + + *notify = ops->get_vq_notification(vdpa, index); + + return 0; +} + +static vm_fault_t vhost_vdpa_fault(struct vm_fault *vmf) +{ + struct vhost_vdpa *v = vmf->vma->vm_file->private_data; struct vdpa_notification_area notify; struct vm_area_struct *vma = vmf->vma; - u16 index = vma->vm_pgoff; + unsigned long index = vma->vm_pgoff; - notify = ops->get_vq_notification(vdpa, index); + if (vhost_vdpa_get_vq_notification(v, index, ¬ify)) + return VM_FAULT_SIGBUS; return vmf_insert_pfn(vma, vmf->address & PAGE_MASK, PFN_DOWN(notify.addr)); } @@ -1514,8 +1530,6 @@ static int vhost_vdpa_mmap(struct file *file, struct vm_area_struct *vma) return -EINVAL; if (vma->vm_flags & VM_READ) return -EINVAL; - if (index > 65535) - return -EINVAL; if (!ops->get_vq_notification) return -ENOTSUPP; @@ -1523,7 +1537,8 @@ static int vhost_vdpa_mmap(struct file *file, struct vm_area_struct *vma) * support the doorbell which sits on the page boundary and * does not share the page with other registers. */ - notify = ops->get_vq_notification(vdpa, index); + if (vhost_vdpa_get_vq_notification(v, index, ¬ify)) + return -EINVAL; if (notify.addr & (PAGE_SIZE - 1)) return -EINVAL; if (vma->vm_end - vma->vm_start != notify.size) -- 2.39.5 (Apple Git-154)