Commit 2fa24d02 authored Oct 12, 2022 by Luís Henriques Committed by Greg Kroah-Hartman Nov 10, 2022

ext4: fix BUG_ON() when directory entry has invalid rec_len

commit 17a0bc9bd697f75cfdf9b378d5eb2d7409c91340 upstream.

The rec_len field in the directory entry has to be a multiple of 4.  A
corrupted filesystem image can be used to hit a BUG() in
ext4_rec_len_to_disk(), called from make_indexed_dir().

 ------------[ cut here ]------------
 kernel BUG at fs/ext4/ext4.h:2413!
 ...
 RIP: 0010:make_indexed_dir+0x53f/0x5f0
 ...
 Call Trace:
  <TASK>
  ? add_dirent_to_buf+0x1b2/0x200
  ext4_add_entry+0x36e/0x480
  ext4_add_nondir+0x2b/0xc0
  ext4_create+0x163/0x200
  path_openat+0x635/0xe90
  do_filp_open+0xb4/0x160
  ? __create_object.isra.0+0x1de/0x3b0
  ? _raw_spin_unlock+0x12/0x30
  do_sys_openat2+0x91/0x150
  __x64_sys_open+0x6c/0xa0
  do_syscall_64+0x3c/0x80
  entry_SYSCALL_64_after_hwframe+0x46/0xb0

The fix simply adds a call to ext4_check_dir_entry() to validate the
directory entry, returning -EFSCORRUPTED if the entry is invalid.

CC: stable@kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216540


Signed-off-by: Luís Henriques <lhenriques@suse.de>
Link: https://lore.kernel.org/r/20221012131330.32456-1-lhenriques@suse.de


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 72743d55

fs/ext4/namei.c

+9 −1

Original line number	Original line	Diff line number	Diff line
	@@ -2141,8 +2141,16 @@ static int make_indexed_dir(handle_t handle, struct ext4_filename fname,
	memcpy(data2, de, len);		memcpy(data2, de, len);
	de = (struct ext4_dir_entry_2 *) data2;		de = (struct ext4_dir_entry_2 *) data2;
	top = data2 + len;		top = data2 + len;
	while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top)		while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top) {
			if (ext4_check_dir_entry(dir, NULL, de, bh2, data2, len,
			(data2 + (blocksize - csum_size) -
			(char *) de))) {
			brelse(bh2);
			brelse(bh);
			return -EFSCORRUPTED;
			}
	de = de2;		de = de2;
			}
	de->rec_len = ext4_rec_len_to_disk(data2 + (blocksize - csum_size) -		de->rec_len = ext4_rec_len_to_disk(data2 + (blocksize - csum_size) -
	(char *) de, blocksize);		(char *) de, blocksize);