iomap: guard io_size EOF trim against concurrent truncate underflow
CVE-2026-72367 · published 15 Aug 2026
How serious is it
- Severity: high, CVSS score 8.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-72367?
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Who is affected
- Linux Linux: 82c59a86a247a8970d353d10f52a37e5564fb137 to < cc1d6af0bee27d6595908b497424f338161299fc, 51d20d1dacbec589d459e11fc88fbca419f84a99 to < 1f38f65bf965fce9aa159d45c5347538f56c5973, 51d20d1dacbec589d459e11fc88fbca419f84a99 to < 7f7780abb4c0fdc9a2603aea8e985ff14ee900e0, 51d20d1dacbec589d459e11fc88fbca419f84a99 to < 55ec50d046c03b3724741957f7b007856e36dbe7
- Linux Linux: 6.13
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
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- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
In the Linux kernel, the following vulnerability has been resolved:
iomap: guard io_size EOF trim against concurrent truncate underflow
iomap: fix zero padding data issue in concurrent append writes
changed ioend accounting so that io_size tracks only valid data
within EOF. This trims io_size when a writeback range extends
past end_pos:
ioend->io_size += map_len;
if (ioend->io_offset + ioend->io_size > end_pos)
ioend->io_size = end_pos - ioend->io_offset;
However, if end_pos ends up below ioend->io_offset, the subtraction
becomes negative and is stored in size_t io_size, causing an unsigned
wrap to a huge value. This can happen when writeback continues past
byte-level EOF up to a block-aligned range, or when a concurrent
truncate shrinks the file after end_pos was sampled in
iomap_writeback_handle_eof().
A wrapped io_size can mislead append detection and corrupt
completion-time size handling, since filesystem end_io paths consume
io_size for decisions such as on-disk EOF updates and unwritten/COW
completion ranges.
Fix this by clamping io_size to zero when EOF has moved to or before
the ioend start offset. This preserves the original intent of trimming
io_size to valid in-EOF data while avoiding the underflow.
Check your whole app
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References
- git.kernel.org/stable/c/cc1d6af0bee27d6595908b497424f338161299fc
- git.kernel.org/stable/c/1f38f65bf965fce9aa159d45c5347538f56c5973
- git.kernel.org/stable/c/7f7780abb4c0fdc9a2603aea8e985ff14ee900e0
- git.kernel.org/stable/c/55ec50d046c03b3724741957f7b007856e36dbe7
Merged from CVE List. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON