Copyright © 2012 Red Hat, Inc. All rights reserved. Low 2026-09-11T00:00:00 kernel: cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-787

In the Linux kernel, the following vulnerability has been resolved: cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 With len == 0 (clone to EOF), the effective length is computed as: len = src_inode->i_size - off; If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent. Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep().

A flaw was found in the Linux kernel's Common Internet File System (CIFS) implementation. When performing a file range remapping operation with a zero length, an integer underflow can occur if the offset exceeds the file size. This can lead to corruption of the byte count in file system control requests, potentially causing unexpected behavior or data integrity issues. The vulnerability is resolved by correctly validating the offset against the file size before calculating the length, preventing the underflow.

Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 10 Fix deferred kernel-rt 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 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-89640 https://nvd.nist.gov/vuln/detail/CVE-2026-89640 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89640.mbox