CVE-2024-38583

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

nilfs2: fix use-after-free of timer for log writer thread

Patch series nilfs2: fix log writer related issues.

This bug fix series covers three nilfs2 log writer-related issues, including a timer use-after-free issue and potential deadlock issue on unmount, and a potential freeze issue in event synchronization found during their analysis. Details are described in each commit log.

This patch (of 3):

A use-after-free issue has been reported regarding the timer sc_timer on the nilfs_sc_info structure.

The problem is that even though it is used to wake up a sleeping log writer thread, sc_timer is not shut down until the nilfs_sc_info structure is about to be freed, and is used regardless of the threads lifetime.

Fix this issue by limiting the use of sc_timer only while the log writer thread is alive.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/2f12b2c03c5dae1a0de0a9e5853177e3d6eee3c6
• https://git.kernel.org/stable/c/67fa90d4a2ccd9ebb0e1e168c7d0b5d0cf3c7148
• https://git.kernel.org/stable/c/68e738be5c518fc3c4e9146b66f67c8fee0135fb
• https://git.kernel.org/stable/c/822ae5a8eac30478578a75f7e064f0584931bf2d
• https://git.kernel.org/stable/c/82933c84f188dcfe89eb26b0b48ab5d1ca99d164
• https://git.kernel.org/stable/c/86a30d6302deddb9fb97ba6fc4b04d0e870b582a
• https://git.kernel.org/stable/c/e65ccf3a4de4f0c763d94789615b83e11f204438
• https://git.kernel.org/stable/c/f5d4e04634c9cf68bdf23de08ada0bb92e8befe7
• https://git.kernel.org/stable/c/f9186bba4ea282b07293c1c892441df3a5441cb0