CVE-2024-42105 Information

Jul 31, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

nilfs2: fix inode number range checks

Patch series ilfs2: 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 ilfs->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 s_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 ilfs->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 s_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.

Reference

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