--- /dev/null
+From a9e1ddc09ca55746079cc479aa3eb6411f0d99d4 Mon Sep 17 00:00:00 2001
+From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
+Date: Sat, 29 Jun 2024 01:51:07 +0900
+Subject: nilfs2: fix kernel bug on rename operation of broken directory
+
+From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
+
+commit a9e1ddc09ca55746079cc479aa3eb6411f0d99d4 upstream.
+
+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: 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ fs/nilfs2/dir.c | 32 ++++++++++++++++++++++++++++++--
+ 1 file changed, 30 insertions(+), 2 deletions(-)
+
+--- a/fs/nilfs2/dir.c
++++ b/fs/nilfs2/dir.c
+@@ -396,11 +396,39 @@ found:
+
+ struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct page **p)
+ {
+- struct nilfs_dir_entry *de = nilfs_get_page(dir, 0, p);
++ struct page *page;
++ struct nilfs_dir_entry *de, *next_de;
++ size_t limit;
++ char *msg;
+
++ de = nilfs_get_page(dir, 0, &page);
+ if (IS_ERR(de))
+ return NULL;
+- return nilfs_next_entry(de);
++
++ limit = nilfs_last_byte(dir, 0); /* is a multiple of chunk size */
++ if (unlikely(!limit || le64_to_cpu(de->inode) != dir->i_ino ||
++ !nilfs_match(1, ".", de))) {
++ msg = "missing '.'";
++ goto fail;
++ }
++
++ next_de = nilfs_next_entry(de);
++ /*
++ * If "next_de" has not reached the end of the chunk, there is
++ * at least one more record. Check whether it matches "..".
++ */
++ if (unlikely((char *)next_de == (char *)de + nilfs_chunk_size(dir) ||
++ !nilfs_match(2, "..", next_de))) {
++ msg = "missing '..'";
++ goto fail;
++ }
++ *p = page;
++ return next_de;
++
++fail:
++ nilfs_error(dir->i_sb, "directory #%lu %s", dir->i_ino, msg);
++ nilfs_put_page(page);
++ return NULL;
+ }
+
+ ino_t nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr)