Lukas Czerner 9d50659406 ext4: fix NULL pointer dereference when journal restart fails ... Currently when journal restart fails, we'll have the h_transaction of the handle set to NULL to indicate that the handle has been effectively aborted. We handle this situation quietly in the jbd2_journal_stop() and just free the handle and exit because everything else has been done before we attempted (and failed) to restart the journal. Unfortunately there are a number of problems with that approach introduced with commit 41a5b91319 "jbd2: invalidate handle if jbd2_journal_restart() fails" First of all in ext4 jbd2_journal_stop() will be called through __ext4_journal_stop() where we would try to get a hold of the superblock by dereferencing h_transaction which in this case would lead to NULL pointer dereference and crash. In addition we're going to free the handle regardless of the refcount which is bad as well, because others up the call chain will still reference the handle so we might potentially reference already freed memory. Moreover it's expected that we'll get aborted handle as well as detached handle in some of the journalling function as the error propagates up the stack, so it's unnecessary to call WARN_ON every time we get detached handle. And finally we might leak some memory by forgetting to free reserved handle in jbd2_journal_stop() in the case where handle was detached from the transaction (h_transaction is NULL). Fix the NULL pointer dereference in __ext4_journal_stop() by just calling jbd2_journal_stop() quietly as suggested by Jan Kara. Also fix the potential memory leak in jbd2_journal_stop() and use proper handle refcounting before we attempt to free it to avoid use-after-free issues. And finally remove all WARN_ON(!transaction) from the code so that we do not get random traces when something goes wrong because when journal restart fails we will get to some of those functions. Cc: stable@vger.kernel.org Signed-off-by: Lukas Czerner <lczerner@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz>		2015-05-14 18:55:18 -04:00
..
checkpoint.c	jbd2: simplify calling convention around __jbd2_journal_clean_checkpoint_list	2014-09-18 00:58:12 -04:00
commit.c	jbd2: fix descriptor block size handling errors with journal_csum	2014-08-28 22:22:29 -04:00
journal.c	Lots of bugs fixes, including Zheng and Jan's extent status shrinker	2014-12-12 09:28:03 -08:00
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
recovery.c	jbd2: complain about descriptor block checksum errors	2015-01-19 15:59:58 -05:00
revoke.c	jbd2: use a better hash function for the revoke table	2014-10-30 10:53:17 -04:00
transaction.c	ext4: fix NULL pointer dereference when journal restart fails	2015-05-14 18:55:18 -04:00