vduse: check that offset is within bounds in get_config()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: vduse: check that offset is within bounds in get_config() This condition checks "len" but it does not check "offset" and that could result in an out of bounds read if "offset > dev->config_size". The problem is that since both variables are unsigned the "dev->config_size - offset" subtraction would result in a very high unsigned value. I think these checks might not be necessary because "len" and "offset" are supposed to already have been validated using the vhost_vdpa_config_validate() function. But I do not know the code perfectly, and I like to be safe.

References

• https://git.kernel.org/stable/c/ebbbc5fea3f648175df1aa3f127c78eb0252cc2a
• https://git.kernel.org/stable/c/dc1db0060c02d119fd4196924eff2d1129e9a442