vhost: block speculation of translated descriptors

iovec addresses coming from vhost are assumed to be pre-validated, but in fact can be speculated to a value out of range. Userspace address are later validated with array_index_nospec so we can be sure kernel info does not leak through these addresses, but vhost must also not leak userspace info outside the allowed memory table to guests. Following the defence in depth principle, make sure the address is not validated out of node range. Signed-off-by: Michael S. Tsirkin <[email protected]> Cc: [email protected] Acked-by: Jason Wang <[email protected]> Tested-by: Jason Wang <[email protected]>
niw · Sep 11, 2019 · a89db44 · a89db44
1 parent cf8f169
commit a89db44
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
@@ -2071,8 +2071,10 @@ static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
 		_iov = iov + ret;
 		size = node->size - addr + node->start;
 		_iov->iov_len = min((u64)len - s, size);
-		_iov->iov_base = (void __user *)(unsigned long)
-			(node->userspace_addr + addr - node->start);
+		_iov->iov_base = (void __user *)
+			((unsigned long)node->userspace_addr +
+			 array_index_nospec((unsigned long)(addr - node->start),
+					    node->size));
 		s += size;
 		addr += size;
 		++ret;