Bug 2541319 (CVE-2026-98126) - CVE-2026-98126 kernel: smb/client: validate new EOF for zero range
Summary: CVE-2026-98126 kernel: smb/client: validate new EOF for zero range
Keywords:
Status: NEW
Alias: CVE-2026-98126
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-25 11:23 UTC by OSIDB Bzimport
Modified: 2026-09-28 13:50 UTC (History)
17 users (show)

Fixed In Version:
Clone Of:
Environment:
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Description OSIDB Bzimport 2026-09-25 11:23:07 UTC
In the Linux kernel, the following vulnerability has been resolved:

smb/client: validate new EOF for zero range

When FALLOC_FL_ZERO_RANGE is used without FALLOC_FL_KEEP_SIZE,
smb3_zero_range() may extend EOF without checking RLIMIT_FSIZE, allowing
the file to grow beyond the caller's file-size limit.

Fix this by calling inode_newsize_ok() before sending the zero-range
request when the operation would extend EOF.

Reproducer, using a file on a CIFS mount:

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

	        trap "" SIGXFSZ
	        ulimit -f 3072

	        truncate -s 2M "$FILE"
	        fallocate --zero-range -o 0 -l 4M "$FILE"
	        echo "fallocate rc=$?"
	        stat -c "file size=%s" "$FILE"
	'

Before this change, the operation succeeds despite the 3 MiB limit:

	fallocate rc=0
	file size=4194304

After this change, fallocate fails and leaves the file at 2 MiB.


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