CVE-2024-53143

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

fsnotify: Fix ordering of iput() and watched_objects decrement

Ensure the superblock is kept alive until were done with iput(). Holding a reference to an inode is not allowed unless we ensure the superblock stays alive, which fsnotify does by keeping the watched_objects count elevated, so iput() must happen before the watched_objects decrement. This can lead to a UAF of something like sb->s_fs_info in tmpfs, but the UAF is hard to hit because race orderings that oops are more likely, thanks to the CHECK_DATA_CORRUPTION() block in generic_shutdown_super().

Also, ensure that fsnotify_put_sb_watched_objects() doesnt call fsnotify_sb_watched_objects() on a superblock that may have already been freed, which would cause a UAF read of sb->s_fsnotify_info.

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 Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.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/21d1b618b6b9da46c5116c640ac4b1cc8d40d63a
• https://git.kernel.org/stable/c/45a8f8232a495221ed058191629f5c628f21601a
• https://git.kernel.org/stable/c/83af1cfa10d9aafdabd06b3655e07727f373b434
• https://project-zero.issues.chromium.org/issues/379667898