nilfs2: fix nilfs_empty_dir() misjudgment and long loop on I/O errors

stable inclusion
from stable-v6.6.35
commit d18b05eda7fa77f02114f15b02c009f28ee42346
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IA8AIS
CVE: CVE-2024-39469

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d18b05eda7fa77f02114f15b02c009f28ee42346

--------------------------------

[ Upstream commit 7373a51e7998b508af7136530f3a997b286ce81c ]

The error handling in nilfs_empty_dir() when a directory folio/page read
fails is incorrect, as in the old ext2 implementation, and if the
folio/page cannot be read or nilfs_check_folio() fails, it will falsely
determine the directory as empty and corrupt the file system.

In addition, since nilfs_empty_dir() does not immediately return on a
failed folio/page read, but continues to loop, this can cause a long loop
with I/O if i_size of the directory's inode is also corrupted, causing the
log writer thread to wait and hang, as reported by syzbot.

Fix these issues by making nilfs_empty_dir() immediately return a false
value (0) if it fails to get a directory folio/page.

Link: https://lkml.kernel.org/r/20240604134255.7165-1-konishi.ryusuke@gmail.com


Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by:  <syzbot+c8166c541d3971bf6c87@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=c8166c541d3971bf6c87


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: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yu Liao <liaoyu15@huawei.com>