CVE-2024-38582

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

nilfs2: fix potential hang in nilfs_detach_log_writer()

Syzbot has reported a potential hang in nilfs_detach_log_writer() called during nilfs2 unmount.

Analysis revealed that this is because nilfs_segctor_sync(), which synchronizes with the log writer thread, can be called after nilfs_segctor_destroy() terminates that thread, as shown in the call trace below:

nilfs_detach_log_writer nilfs_segctor_destroy nilfs_segctor_kill_thread –> Shut down log writer thread flush_work nilfs_iput_work_func nilfs_dispose_list iput nilfs_evict_inode nilfs_transaction_commit nilfs_construct_segment (if inode needs sync) nilfs_segctor_sync –> Attempt to synchronize with log writer thread *** DEADLOCK ***

Fix this issue by changing nilfs_segctor_sync() so that the log writer thread returns normally without synchronizing after it terminates, and by forcing tasks that are already waiting to complete once after the thread terminates.

The skipped inode metadata flushout will then be processed together in the subsequent cleanup work in nilfs_segctor_destroy().

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/06afce714d87c7cd1dcfccbcd800c5c5d2cf1cfd
• https://git.kernel.org/stable/c/1c3844c5f4eac043954ebf6403fa9fd1f0e9c1c0
• https://git.kernel.org/stable/c/6e5c8e8e024e147b834f56f2115aad241433679b
• https://git.kernel.org/stable/c/911d38be151921a5d152bb55e81fd752384c6830
• https://git.kernel.org/stable/c/a8799662fed1f8747edae87a1937549288baca6a
• https://git.kernel.org/stable/c/bc9cee50a4a4ca23bdc49f75ea8242d8a2193b3b
• https://git.kernel.org/stable/c/c516db6ab9eabbedbc430b4f93b0d8728e9b427f
• https://git.kernel.org/stable/c/eb85dace897c5986bc2f36b3c783c6abb8a4292e
• https://git.kernel.org/stable/c/eff7cdf890b02596b8d73e910bdbdd489175dbdb
• https://git.kernel.org/stable/c/06afce714d87c7cd1dcfccbcd800c5c5d2cf1cfd
• https://git.kernel.org/stable/c/1c3844c5f4eac043954ebf6403fa9fd1f0e9c1c0
• https://git.kernel.org/stable/c/6e5c8e8e024e147b834f56f2115aad241433679b
• https://git.kernel.org/stable/c/911d38be151921a5d152bb55e81fd752384c6830
• https://git.kernel.org/stable/c/a8799662fed1f8747edae87a1937549288baca6a
• https://git.kernel.org/stable/c/bc9cee50a4a4ca23bdc49f75ea8242d8a2193b3b
• https://git.kernel.org/stable/c/c516db6ab9eabbedbc430b4f93b0d8728e9b427f
• https://git.kernel.org/stable/c/eb85dace897c5986bc2f36b3c783c6abb8a4292e
• https://git.kernel.org/stable/c/eff7cdf890b02596b8d73e910bdbdd489175dbdb
• https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html