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Commit ff9767ba authored by Ryusuke Konishi's avatar Ryusuke Konishi Committed by Greg Kroah-Hartman
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nilfs2: fix kernel bug on rename operation of broken directory 

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


Fixes: 2ba466d7 ("nilfs2: directory entry operations")
Tested-by: default avatarRyusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 17866066

fs/nilfs2/dir.c

+30 −2
Original line number Diff line number Diff line
@@ -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)