dma-buf: heaps: Fix off-by-one in CMA heap fault handler

Open Source Vulnerabilities ASB-A-363259128

In cma_heap_vm_fault of cma_heap.c, there is a possible out of bounds write due to improper input validation. This could lead to local escalation of privilege in the kernel with no additional execution privileges needed. User interaction is not needed for exploitation.

Open Source Vulnerabilities CVE-2024-46852

In the Linux kernel, the following vulnerability has been resolved: dma-buf: heaps: Fix off-by-one in CMA heap fault handler Until VM_DONTEXPAND was added in commit 1c1914d6e8c6 ("dma-buf: heaps: Don't track CMA dma-buf pages under RssFile") it was possible to obtain a mapping larger than the buffer size via mremap and bypass the overflow check in dma_buf_mmap_internal. When using such a mapping to attempt to fault past the end of the buffer, the CMA heap fault handler also checks the fault offset against the buffer size, but gets the boundary wrong by 1. Fix the boundary check so that we don't read off the end of the pages array and insert an arbitrary page in the mapping.