nilfs2: fix kernel bug on rename operation of broken directory

stable inclusion
from stable-v4.19.319
commit ff9767ba2cb949701e45e6e4287f8af82986b703
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAGEKP
CVE: CVE-2024-41034

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ff9767ba2cb949701e45e6e4287f8af82986b703

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[ Upstream commit a9e1ddc09ca55746079cc479aa3eb6411f0d99d4 ]

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().

Link: https://lkml.kernel.org/r/20240628165107.9006-1-konishi.ryusuke@gmail.com


Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by:  <syzbot+d3abed1ad3d367fa2627@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=d3abed1ad3d367fa2627


Fixes: 2ba466d7 ("nilfs2: directory entry operations")
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zhihao Cheng <chengzhihao@huaweicloud.com>