CVE-2024-42105

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

nilfs2: fix inode number range checks

Patch series "nilfs2: fix potential issues related to reserved inodes".

This series fixes one use-after-free issue reported by syzbot, caused by

nilfs2's internal inode being exposed in the namespace on a corrupted

filesystem, and a couple of flaws that cause problems if the starting

number of non-reserved inodes written in the on-disk super block is

intentionally (or corruptly) changed from its default value.

This patch (of 3):

In the current implementation of nilfs2, "nilfs->ns_first_ino", which

gives the first non-reserved inode number, is read from the superblock,

but its lower limit is not checked.

As a result, if a number that overlaps with the inode number range of

reserved inodes such as the root directory or metadata files is set in the

super block parameter, the inode number test macros (NILFS_MDT_INODE and

NILFS_VALID_INODE) will not function properly.

In addition, these test macros use left bit-shift calculations using with

the inode number as the shift count via the BIT macro, but the result of a

shift calculation that exceeds the bit width of an integer is undefined in

the C specification, so if "ns_first_ino" is set to a large value other

than the default value NILFS_USER_INO (=11), the macros may potentially

malfunction depending on the environment.

Fix these issues by checking the lower bound of "nilfs->ns_first_ino" and

by preventing bit shifts equal to or greater than the NILFS_USER_INO

constant in the inode number test macros.

Also, change the type of "ns_first_ino" from signed integer to unsigned

integer to avoid the need for type casting in comparisons such as the

lower bound check introduced this time.