This is a note to let you know that I've just added the patch titled ext4: don't try to processed freed blocks until mballoc is initialized to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ext4-don-t-try-to-processed-freed-blocks-until-mball.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 144c3aa759dd8a4d633f4533eeb628ac08696ce6 Author: Theodore Ts'o <tytso@xxxxxxx> Date: Thu Jan 21 12:33:20 2021 -0500 ext4: don't try to processed freed blocks until mballoc is initialized [ 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@xxxxxxx Reported-by: Murphy Zhou <jencce.kernel@xxxxxxxxx> Reviewed-by: Jan Kara <jack@xxxxxxx> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 9a6f9875aa34..2ae0af1c88c7 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4875,7 +4875,6 @@ 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 = @@ -4987,6 +4986,14 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) 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));