Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-08-15T00:00:00 kernel: iomap: guard io_size EOF trim against concurrent truncate underflow 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-191

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.

A flaw was found in the Linux kernel's iomap subsystem. This vulnerability occurs due to an integer underflow when calculating io_size during concurrent file truncation operations. If a file is truncated while writeback is in progress, the io_size can wrap to a large value, leading to incorrect handling of file data. This can result in data corruption within the filesystem.

Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Not affected kernel Red Hat Enterprise Linux 8 Not affected kernel-rt Red Hat Enterprise Linux 9 Not affected kernel Red Hat Enterprise Linux 9 Not affected kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-72367 https://nvd.nist.gov/vuln/detail/CVE-2026-72367 https://lore.kernel.org/linux-cve-announce/2026081515-CVE-2026-72367-6c0f@gregkh/T