CVE-2026-98126 in Linux
Summary
by MITRE • 09/25/2026
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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