Description
In the Linux kernel, the following vulnerability has been resolved:

smb/client: validate new EOF for insert range

smb3_insert_range() does not check if the new file size
(i_size + len) is valid. This allows FALLOC_FL_INSERT_RANGE to bypass
RLIMIT_FSIZE, exceed s_maxbytes, or produce a size outside the loff_t
range.

Use check_add_overflow() to calculate the new EOF. Validate it with
inode_newsize_ok() before modifying the file.

Reproducer, using a file on a CIFS mount:

bash -c '
FILE=/mnt/cifs/repro

trap "" SIGXFSZ
ulimit -f 3072 # RLIMIT_FSIZE = 3 MiB

# A regular write is stopped at 3 MiB.
dd if=/dev/zero of="$FILE" bs=1M count=4 status=none
stat -c "size after write: %s" "$FILE"

# Insert 2 MiB into a 2 MiB file.
truncate -s 2M "$FILE"
fallocate -i -o 0 -l 2M "$FILE"
stat -c "size after insert: %s" "$FILE"
'

Before this change, the regular write stops at the 3 MiB limit, but
insert range grows the file to 4 MiB:

dd: error writing '/mnt/cifs/repro': File too large
size after write: 3145728
size after insert: 4194304

After this change, insert range also fails at the limit and leaves the
2 MiB file unchanged:

dd: error writing '/mnt/cifs/repro': File too large
size after write: 3145728
fallocate: fallocate failed: File too large
size after insert: 2097152
Published: 2026-09-25
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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History

Fri, 25 Sep 2026 12:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-190

Fri, 25 Sep 2026 10:45:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: smb/client: validate new EOF for insert range smb3_insert_range() does not check if the new file size (i_size + len) is valid. This allows FALLOC_FL_INSERT_RANGE to bypass RLIMIT_FSIZE, exceed s_maxbytes, or produce a size outside the loff_t range. Use check_add_overflow() to calculate the new EOF. Validate it with inode_newsize_ok() before modifying the file. Reproducer, using a file on a CIFS mount: bash -c ' FILE=/mnt/cifs/repro trap "" SIGXFSZ ulimit -f 3072 # RLIMIT_FSIZE = 3 MiB # A regular write is stopped at 3 MiB. dd if=/dev/zero of="$FILE" bs=1M count=4 status=none stat -c "size after write: %s" "$FILE" # Insert 2 MiB into a 2 MiB file. truncate -s 2M "$FILE" fallocate -i -o 0 -l 2M "$FILE" stat -c "size after insert: %s" "$FILE" ' Before this change, the regular write stops at the 3 MiB limit, but insert range grows the file to 4 MiB: dd: error writing '/mnt/cifs/repro': File too large size after write: 3145728 size after insert: 4194304 After this change, insert range also fails at the limit and leaves the 2 MiB file unchanged: dd: error writing '/mnt/cifs/repro': File too large size after write: 3145728 fallocate: fallocate failed: File too large size after insert: 2097152
Title smb/client: validate new EOF for insert range
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-25T10:36:08.406Z

Reserved: 2026-09-25T10:25:14.318Z

Link: CVE-2026-98127

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-25T11:17:44.050

Modified: 2026-09-25T11:17:44.050

Link: CVE-2026-98127

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-25T12:30:08Z

Weaknesses