AZL-75129

In the Linux kernel, the following vulnerability has been resolved:

dm-verity: disable recursive forward error correction

There are two problems with the recursive correction:

1. It may cause denial-of-service. In fecreadbufs, there is a loop that has 253 iterations. For each iteration, we may call verityhashfor_block recursively. There is a limit of 4 nested recursions - that means that there may be at most 253^4 (4 billion) iterations. Red Hat QE team actually created an image that pushes dm-verity to this limit - and this image just makes the udev-worker process get stuck in the 'D' state.

2. It doesn't work. In fecreadbufs we store data into the variable "fio->bufs", but fio bufs is shared between recursive invocations, if "verityhashfor_block" invoked correction recursively, it would overwrite partially filled fio->bufs.