CVE-2025-38627

Published: August 23, 2025Last modified: August 23, 2025

Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: compress: fix UAF of f2fs_inode_info in f2fs_free_dic The decompress_io_ctx may be released asynchronously after I/O completion. If this file is deleted immediately after read, and the kworker of processing post_read_wq has not been executed yet due to high workloads, It is possible that the inode(f2fs_inode_info) is evicted and freed before it is used f2fs_free_dic. The UAF case as below: Thread A Thread B - f2fs_decompress_end_io - f2fs_put_dic - queue_work add free_dic work to post_read_wq - do_unlink - iput - evict - call_rcu This file is deleted after read. Thread C kworker to process post_read_wq - rcu_do_batch - f2fs_free_inode - kmem_cache_free inode is freed by rcu - process_scheduled_works - f2fs_late_free_dic - f2fs_free_dic - f2fs_release_decomp_mem read (dic->inode)->i_compress_algorithm This patch store compress_algorithm and sbi in dic to avoid inode UAF. In addition, the previous solution is deprecated in [1] may cause system hang. [1] https://lore.kernel.org/all/[email protected]

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References

• https://git.kernel.org/stable/c/39868685c2a94a70762bc6d77dc81d781d05bff5
• https://git.kernel.org/stable/c/5d604d40cd3232b09cb339941ef958e49283ed0a
• https://git.kernel.org/stable/c/8fae5b6addd5f6895e03797b56e3c7b9f9cd15c9