CVE-2024-36019: Out-of-bounds Read

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

regmap: maple: Fix cache corruption in regcache_maple_drop()

When keeping the upper end of a cache block entry, the entry[] array must be indexed by the offset from the base register of the block, i.e. max - mas.index.

The code was indexing entry[] by only the register address, leading to an out-of-bounds access that copied some part of the kernel memory over the cache contents.

This bug was not detected by the regmap KUnit test because it only tests with a block of registers starting at 0, so mas.index == 0.