CVE-2025-71237

Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: Fix potential block overflow that cause system hang When a user executes the FITRIM command, an underflow can occur when calculating nblocks if end_block is too small. Since nblocks is of type sector_t, which is u64, a negative nblocks value will become a very large positive integer. This ultimately leads to the block layer function __blkdev_issue_discard() taking an excessively long time to process the bio chain, and the ns_segctor_sem lock remains held for a long period. This prevents other tasks from acquiring the ns_segctor_sem lock, resulting in the hang reported by syzbot in [1]. If the ending block is too small, typically if it is smaller than 4KiB range, depending on the usage of the segment 0, it may be possible to attempt a discard request beyond the device size causing the hang. Exiting successfully and assign the discarded size (0 in this case) to range->len. Although the start and len values in the user input range are too small, a conservative strategy is adopted here to safely ignore them, which is equivalent to a no-op; it will not perform any trimming and will not throw an error. [1] task:segctord state:D stack:28968 pid:6093 tgid:6093 ppid:2 task_flags:0x200040 flags:0x00080000 Call Trace: rwbase_write_lock+0x3dd/0x750 kernel/locking/rwbase_rt.c:272 nilfs_transaction_lock+0x253/0x4c0 fs/nilfs2/segment.c:357 nilfs_segctor_thread_construct fs/nilfs2/segment.c:2569 [inline] nilfs_segctor_thread+0x6ec/0xe00 fs/nilfs2/segment.c:2684 [ryusuke: corrected part of the commit message about the consequences]

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• Patch details

Patch details

References

• MITRE
• NVD
• Launchpad
• Debian

Other references

• https://www.cve.org/CVERecord?id=CVE-2025-71237
• https://git.kernel.org/stable/c/4aa45f841413cca81882602b4042c53502f34cad
• https://git.kernel.org/stable/c/b8c5ee234bd54f1447c846101fdaef2cf70c2149
• https://git.kernel.org/stable/c/df1e20796c9f3d541cca47fb72e4369ea135642d
• https://git.kernel.org/stable/c/ea2278657ad0d62596589fbe2caf995e189e65e7