[bug report] libnvdimm: control (ioctl) messages for nvdimm_bus and nvdimm devices

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Dan Williams,

The patch 62232e45f4a2: "libnvdimm: control (ioctl) messages for
nvdimm_bus and nvdimm devices" from Jun 8, 2015, leads to the
following static checker warning:

	drivers/acpi/nfit/core.c:611 acpi_nfit_ctl()
	error: 'out_size' from user is not capped properly

drivers/acpi/nfit/core.c
   594          for (i = 0, offset = 0; i < desc->out_num; i++) {
   595                  u32 out_size = nd_cmd_out_size(nvdimm, cmd, desc, i, buf,
   596                                  (u32 *) out_obj->buffer.pointer,
   597                                  out_obj->buffer.length - offset);
   598  
   599                  if (offset + out_size > out_obj->buffer.length) {
                            ^^^^^^^^^^^^^^^^^
It looks like this addition could have an integer overflow bug.

   600                          dev_dbg(dev, "%s output object underflow cmd: %s field: %d\n",
   601                                          dimm_name, cmd_name, i);
   602                          break;
   603                  }
   604  
   605                  if (in_buf.buffer.length + offset + out_size > buf_len) {
                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The comments suggest that this is safe.  I don't know the code.

   606                          dev_dbg(dev, "%s output overrun cmd: %s field: %d\n",
   607                                          dimm_name, cmd_name, i);
   608                          rc = -ENXIO;
   609                          goto out;
   610                  }
   611                  memcpy(buf + in_buf.buffer.length + offset,
   612                                  out_obj->buffer.pointer + offset, out_size);
   613                  offset += out_size;
   614          }
   615  

regards,
dan carpenter