In the Linux kernel, the following vulnerability has been resolved:
ksmbd: Do not skip lock checks for single-byte ranges
check_lock_range() uses inclusive ranges. Its callers pass the end
offset as start + length – 1, so start == end represents a valid
single-byte range rather than an empty range.
The start == end shortcut therefore skips mandatory byte-range lock
checks for one-byte reads, writes, copychunk operations and one-byte
truncate ranges. A conflicting lock covering that byte is not checked
and the operation is allowed to proceed.
Remove the shortcut. The truncate size == inode->i_size case is already
handled by only calling check_lock_range() when the new size differs
from the current file size.
