fs/vfs: check buffer count and pointer for iovec

There are iovecs provided by user such as readv().

Signed-off-by: wangjianyu3 <wangjianyu3@xiaomi.com>

fs/vfs/fs_read.c

@@ -164,6 +164,18 @@ ssize_t file_readv(FAR struct file *filep,
   DEBUGASSERT(filep);
   inode = filep->f_inode;
 
+  /* Check buffer count and pointer for iovec */
+
+  if (iovcnt == 0)
+    {
+      return 0;
+    }
+
+  if (iov == NULL)
+    {
+      return -EFAULT;
+    }
+
   /* Are all iov_base accessible? */
 
   for (ret = 0; ret < iovcnt; ret++)

fs/vfs/fs_write.c

@@ -153,6 +153,18 @@ ssize_t file_writev(FAR struct file *filep,
       return -EACCES;
     }
 
+  /* Check buffer count and pointer for iovec */
+
+  if (iovcnt == 0)
+    {
+      return 0;
+    }
+
+  if (iov == NULL)
+    {
+      return -EFAULT;
+    }
+
   /* Are all iov_base accessible? */
 
   for (ret = 0; ret < iovcnt; ret++)