nilfs2: fix kernel bug on rename operation of broken directory

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix kernel bug on rename operation of broken directory Syzbot reported that in rename directory operation on broken directory on nilfs2, __block_write_begin_int() called to prepare block write may fail BUG_ON check for access exceeding the folio/page size. This is because nilfs_dotdot(), which gets parent directory reference entry ("..") of the directory to be moved or renamed, does not check consistency enough, and may return location exceeding folio/page size for broken directories. Fix this issue by checking required directory entries ("." and "..") in the first chunk of the directory in nilfs_dotdot().

References

• https://git.kernel.org/stable/c/ff9767ba2cb949701e45e6e4287f8af82986b703
• https://git.kernel.org/stable/c/24c1c8566a9b6be51f5347be2ea76e25fc82b11e
• https://git.kernel.org/stable/c/a9a466a69b85059b341239766a10efdd3ee68a4b
• https://git.kernel.org/stable/c/7000b438dda9d0f41a956fc9bffed92d2eb6be0d
• https://git.kernel.org/stable/c/1a8879c0771a68d70ee2e5e66eea34207e8c6231
• https://git.kernel.org/stable/c/60f61514374e4a0c3b65b08c6024dd7e26150bfd
• https://git.kernel.org/stable/c/298cd810d7fb687c90a14d8f9fd1b8719a7cb8a5
• https://git.kernel.org/stable/c/a9e1ddc09ca55746079cc479aa3eb6411f0d99d4