Vulnerability CVE-2024-42105
Published: 2024-07-30

Description:
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.

 References:
https://git.kernel.org/stable/c/57235c3c88bb430043728d0d02f44a4efe386476
https://git.kernel.org/stable/c/08cab183a624ba71603f3754643ae11cab34dbc4
https://git.kernel.org/stable/c/731011ac6c37cbe97ece229fc6daa486276052c5
https://git.kernel.org/stable/c/3be4dcc8d7bea52ea41f87aa4bbf959efe7a5987
https://git.kernel.org/stable/c/fae1959d6ab2c52677b113935e36ab4e25df37ea
https://git.kernel.org/stable/c/9194f8ca57527958bee207919458e372d638d783
https://git.kernel.org/stable/c/1c91058425a01131ea30dda6cf43c67b17884d6a
https://git.kernel.org/stable/c/e2fec219a36e0993642844be0f345513507031f4
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