nilfs2: fix use-after-free bug of nilfs_root in nilfs_evict_inode()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix use-after-free bug of nilfs_root in nilfs_evict_inode() During unmount process of nilfs2, nothing holds nilfs_root structure after nilfs2 detaches its writer in nilfs_detach_log_writer(). However, since nilfs_evict_inode() uses nilfs_root for some cleanup operations, it may cause use-after-free read if inodes are left in "garbage_list" and released by nilfs_dispose_list() at the end of nilfs_detach_log_writer(). Fix this issue by modifying nilfs_evict_inode() to only clear inode without additional metadata changes that use nilfs_root if the file system is degraded to read-only or the writer is detached.

References

• https://git.kernel.org/stable/c/f31e18131ee2ce80a4da5c808221d25b1ae9ad6d
• https://git.kernel.org/stable/c/2a782ea8ebd712a458466e3103e2881b4f886cb5
• https://git.kernel.org/stable/c/116d53f09ff52e6f98e3fe1f85d8898d6ba26c68
• https://git.kernel.org/stable/c/6b4205ea97901f822004e6c8d59484ccfda03faa
• https://git.kernel.org/stable/c/b8427b8522d9ede53015ba45a9978ba68d1162f5
• https://git.kernel.org/stable/c/acc2a40e428f12780004e1e9fce4722d88f909fd
• https://git.kernel.org/stable/c/fb8e8d58f116d069e5939e1f786ac84e7fa4533e
• https://git.kernel.org/stable/c/9b5a04ac3ad9898c4745cba46ea26de74ba56a8e