CVE-2024-36883

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

net: fix out-of-bounds access in ops_init

netallocgeneric is called by netalloc, which is called without any locking. It reads maxgenptrs, which is changed under pernetops_rwsem. It is read twice, first to allocate an array, then to set s.len, which is later used to limit the bounds of the array access.

It is possible that the array is allocated and another thread is registering a new pernet ops, increments maxgenptrs, which is then used to set s.len with a larger than allocated length for the variable array.

Fix it by reading maxgenptrs only once in netallocgeneric. If maxgenptrs is later incremented, it will be caught in netassigngeneric.