Affected: Linux

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.