Executive Summary

This vulnerability is a use-after-free race condition in the Linux kernel's md (multiple device) subsystem, specifically in the bitmap handling code. It occurs during the resizing of an array in the write_page() function, where a General Protection Fault (GPF) can happen.

The issue arises because the bitmap_daemon_work() function iterates over bitmap->storage.filemap without proper locking, while at the same time, the __bitmap_resize() function can free that storage via md_bitmap_file_unmap(). The quiesce() function does not stop the md thread, allowing concurrent access to memory that has already been freed.

The fix involves holding the mddev->bitmap_info.mutex during bitmap updates to prevent this race condition.

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Impact Analysis

This vulnerability can cause a General Protection Fault in the Linux kernel, which may lead to system instability or crashes. Because it is a use-after-free race condition, it could potentially be exploited to cause unpredictable behavior or denial of service by triggering the kernel to access freed memory.

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Mitigation Strategies

The vulnerability is fixed by holding the mddev->bitmap_info.mutex during the bitmap update to prevent the use-after-free race condition.

Immediate mitigation steps include updating the Linux kernel to a version that contains this fix.

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