From: Theodore Ts'o <tytso@mit.edu> mainline inclusion from mainline-v5.12-rc1 commit 027f14f5357279655c3ebc6d14daff8368d4f53f category: bugfix bugzilla: 46758 CVE: NA ----------------------------------------------- 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> conflicts: fs/ext4/super.c Signed-off-by: Ye Bin <yebin10@huawei.com> Reviewed-by: zhangyi (F) <yi.zhang@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- fs/ext4/super.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 6b93f83564bdd..1e040e0bc4879 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4480,8 +4480,6 @@ 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; - no_journal: if (!test_opt(sb, NO_MBCACHE)) { sbi->s_ea_block_cache = ext4_xattr_create_cache(); @@ -4588,6 +4586,14 @@ 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)); -- 2.25.1