linux/fs/jbd2
Jan Kara ccd3c4373e jbd2: fix use after free in jbd2_log_do_checkpoint()
The code cleaning transaction's lists of checkpoint buffers has a bug
where it increases bh refcount only after releasing
journal->j_list_lock. Thus the following race is possible:

CPU0					CPU1
jbd2_log_do_checkpoint()
					jbd2_journal_try_to_free_buffers()
					  __journal_try_to_free_buffer(bh)
  ...
  while (transaction->t_checkpoint_io_list)
  ...
    if (buffer_locked(bh)) {

<-- IO completes now, buffer gets unlocked -->

      spin_unlock(&journal->j_list_lock);
					    spin_lock(&journal->j_list_lock);
					    __jbd2_journal_remove_checkpoint(jh);
					    spin_unlock(&journal->j_list_lock);
					  try_to_free_buffers(page);
      get_bh(bh) <-- accesses freed bh

Fix the problem by grabbing bh reference before unlocking
journal->j_list_lock.

Fixes: dc6e8d669c ("jbd2: don't call get_bh() before calling __jbd2_journal_remove_checkpoint()")
Fixes: be1158cc61 ("jbd2: fold __process_buffer() into jbd2_log_do_checkpoint()")
Reported-by: syzbot+7f4a27091759e2fe7453@syzkaller.appspotmail.com
CC: stable@vger.kernel.org
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2018-10-05 18:44:40 -04:00
..
Kconfig jbd2: remove debug dependency on debug_fs and update Kconfig help text 2013-06-12 23:07:51 -04:00
Makefile [PATCH] jbd2: rename jbd2 symbols to avoid duplication of jbd symbols 2006-10-11 11:14:15 -07:00
checkpoint.c jbd2: fix use after free in jbd2_log_do_checkpoint() 2018-10-05 18:44:40 -04:00
commit.c jbd2: replace current_kernel_time64 with ktime equivalent 2018-07-29 15:51:47 -04:00
journal.c jbd2: remove NULL check before calling kmem_cache_destroy() 2018-05-20 22:38:26 -04:00
recovery.c jbd2: clarify bad journal block checksum message 2018-02-18 21:33:13 -05:00
revoke.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
transaction.c jbd2: don't mark block as modified if the handle is out of credits 2018-06-16 20:21:45 -04:00