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

[ 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: 2ba466d74ed7 ("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>

diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
index 22f1f75a90c1a0e4258d31fdf80415d5aa94cd47..552234ef22fe729e89754554be434eb04a635eac 100644 (file)
--- a/fs/nilfs2/dir.c
+++ b/fs/nilfs2/dir.c
@@ -627,7 +627,7 @@ int nilfs_empty_dir(struct inode *inode)
 
                kaddr = nilfs_get_page(inode, i, &page);
                if (IS_ERR(kaddr))
-                       continue;
+                       return 0;
 
                de = (struct nilfs_dir_entry *)kaddr;
                kaddr += nilfs_last_byte(inode, i) - NILFS_DIR_REC_LEN(1);