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 nilfs2s 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.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/08cab183a624ba71603f3754643ae11cab34dbc4
• https://git.kernel.org/stable/c/1c91058425a01131ea30dda6cf43c67b17884d6a
• https://git.kernel.org/stable/c/3be4dcc8d7bea52ea41f87aa4bbf959efe7a5987
• https://git.kernel.org/stable/c/57235c3c88bb430043728d0d02f44a4efe386476
• https://git.kernel.org/stable/c/731011ac6c37cbe97ece229fc6daa486276052c5
• https://git.kernel.org/stable/c/9194f8ca57527958bee207919458e372d638d783
• https://git.kernel.org/stable/c/e2fec219a36e0993642844be0f345513507031f4
• https://git.kernel.org/stable/c/fae1959d6ab2c52677b113935e36ab4e25df37ea
• https://git.kernel.org/stable/c/08cab183a624ba71603f3754643ae11cab34dbc4
• https://git.kernel.org/stable/c/1c91058425a01131ea30dda6cf43c67b17884d6a
• https://git.kernel.org/stable/c/3be4dcc8d7bea52ea41f87aa4bbf959efe7a5987
• https://git.kernel.org/stable/c/57235c3c88bb430043728d0d02f44a4efe386476
• https://git.kernel.org/stable/c/731011ac6c37cbe97ece229fc6daa486276052c5
• https://git.kernel.org/stable/c/9194f8ca57527958bee207919458e372d638d783
• https://git.kernel.org/stable/c/e2fec219a36e0993642844be0f345513507031f4
• https://git.kernel.org/stable/c/fae1959d6ab2c52677b113935e36ab4e25df37ea
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html