Linux Kernel up to 7.2.4 f2fs folio_nr_pages i_pages/mapping race condition

Summaryinfo

A vulnerability, which was classified as very critical, was found in Linux Kernel up to 7.2.4. Impacted is the function folio_nr_pages of the component f2fs. Executing a manipulation of the argument i_pages/mapping can lead to race condition. This vulnerability is tracked as CVE-2026-89836. The attack can be launched remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 7.2.4 and classified as very critical. This vulnerability affects the function folio_nr_pages of the component f2fs. The manipulation of the argument i_pages/mapping with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix folio_nr_pages() race after put in large folio invalidate Our v6.18 based Android system is continuely suffering livelock and bad page stat as shown in[1] which related to broken xarray slot status. By investigating big folio operations within f2fs, we find below races and fix it by get the nr_pages before drop the refcount and folio_lock. f2fs_get_read_data_folio() calls f2fs_folio_put() before folio_nr_pages() when invalidating a large folio from the page cache. That unlocks the folio and drops the caller reference, leaving a window where a concurrent truncate or folio split can shrink the compound folio or free it before the invalidate range is computed. An undersized range then leaves split sub-folios in mapping->i_pages, which can later interact badly with truncate and reclaim (stale xarray entries and bad page state when folio->mapping no longer matches the mapping being truncated). [1] PID: 2594 TASK: ffffff8169b81580 CPU: 7 COMMAND: "Thread-3" #0 [ffffffc08ef2b8a0] xas_load at ffffffe52d1f42a4 #1 [ffffffc08ef2b900] find_get_entries at ffffffe52c185798 #2 [ffffffc08ef2bb60] truncate_inode_pages_range at ffffffe52c19e83c #3 [ffffffc08ef2bbc0] truncate_inode_pages_final at ffffffe52c19ec2c #4 [ffffffc08ef2bc20] f2fs_evict_inode at ffffffe52c4c8400 #5 [ffffffc08ef2bcc0] evict at ffffffe52c2de9f4 #6 [ffffffc08ef2bd00] iput at ffffffe52c2db1b4 #7 [ffffffc08ef2bd30] dentry_unlink_inode at ffffffe52c2d7204 #8 [ffffffc08ef2bd50] __dentry_kill at ffffffe52c2d3dcc #9 [ffffffc08ef2bd80] dput at ffffffe52c2d3c3c #10 [ffffffc08ef2bda0] __fput at ffffffe52c2b0a7c #11 [ffffffc08ef2bde0] ____fput at ffffffe52c2b1034 #12 [ffffffc08ef2bdf0] task_work_run at ffffffe52beea200 #13 [ffffffc08ef2be20] exit_to_user_mode_loop at ffffffe52bfbc17c #14 [ffffffc08ef2be80] el0_svc at ffffffe52d1f8e54 #15 [ffffffc08ef2beb0] el0t_64_sync_handler at ffffffe52d1f8d10

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-89836 since 09/11/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/16/2026).

Upgrading to version 7.2.5 or 7.3-rc1 eliminates this vulnerability. Applying the patch cc34df18da92f68f9b384c3ae95ad64be46cb5ee/0dab71381f1b4d12dc2056f8bd5aaa9d93ce9082 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4

License

• open-source

Website

• Vendor: https://www.kernel.org/

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