[PATCH AUTOSEL 5.10 34/47] ext4: don't try to processed freed blocks until mballoc is initialized

Sasha Levin
2021-03-02T13:03:17Z

From: Theodore Ts'o <tytso@mit.edu>

[ Upstream commit 027f14f5357279655c3ebc6d14daff8368d4f53f ]

If we try to make any changes via the journal between when the journal
is initialized, but before the multi-block allocated is initialized,
we will end up deferencing a NULL pointer when the journal commit
callback function calls ext4_process_freed_data().

The proximate cause of this failure was commit 2d01ddc86606 ("ext4:
save error info to sb through journal if available") since file system
corruption problems detected before the call to ext4_mb_init() would
result in a journal commit before we aborted the mount of the file
system.... and we would then trigger the NULL pointer deref.

Link: https://lore.kernel.org/r/YAm8qH/0oo2ofSMR@mit.edu
Reported-by: Murphy Zhou <jencce.kernel@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ext4/super.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ea5aefa23a20..e30bf8f342c2 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4876,7 +4876,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)

set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);

- sbi->s_journal->j_commit_callback = ext4_journal_commit_callback;
sbi->s_journal->j_submit_inode_data_buffers =
ext4_journal_submit_inode_data_buffers;
sbi->s_journal->j_finish_inode_data_buffers =
@@ -4993,6 +4992,14 @@ no_journal:
goto failed_mount5;
}

+ /*
+ * We can only set up the journal commit callback once
+ * mballoc is initialized
+ */
+ if (sbi->s_journal)
+ sbi->s_journal->j_commit_callback =
+ ext4_journal_commit_callback;
+
block = ext4_count_free_clusters(sb);
ext4_free_blocks_count_set(sbi->s_es,
EXT4_C2B(sbi, block));
--
2.30.1