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

Vulnerability Description

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

References

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