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 --- Please apply this patch to the stable trees indicated by the subject prefix instead of the patch that failed.

This patch is tailored to take page/folio conversion into account and can be applied to these stable trees.

Also, all the builds and tests I did on each stable tree passed.

Thanks, Ryusuke Konishi

fs/nilfs2/dir.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c index 51c982ad9608..53e4e63c607e 100644 --- a/fs/nilfs2/dir.c +++ b/fs/nilfs2/dir.c @@ -396,11 +396,39 @@ nilfs_find_entry(struct inode *dir, const struct qstr *qstr,

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)