CVE-2026-43163: Concurrent Execution using Shared Resource with Improper Synchronization

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

md/bitmap: fix GPF in write_page caused by resize race

A General Protection Fault occurs in write_page() during array resize: RIP: 0010:write_page+0x22b/0x3c0 [md_mod]

This is a use-after-free race between bitmap_daemon_work() and __bitmap_resize(). The daemon iterates over `bitmap->storage.filemap` without locking, while the resize path frees that storage via md_bitmap_file_unmap(). `quiesce()` does not stop the md thread, allowing concurrent access to freed pages.

Fix by holding `mddev->bitmap_info.mutex` during the bitmap update.