regmap: maple: Fix cache corruption in regcache_maple_drop()

Vulnerability Description

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.

References

• https://git.kernel.org/stable/c/3af6c5ac72dc5b721058132a0a1d7779e443175e
• https://git.kernel.org/stable/c/51c4440b9d3fd7c8234e6de9170a487c03506e53
• https://git.kernel.org/stable/c/00bb549d7d63a21532e76e4a334d7807a54d9f31