Commit 172e344e authored by Ye Bin's avatar Ye Bin Committed by Theodore Ts'o
Browse files

ext4: init error handle resource before init group descriptors 



Now, 's_err_report' timer is init after ext4_group_desc_init() when fill
super. Theoretically, ext4_group_desc_init() may access to error handle
as follows:
__ext4_fill_super
  ext4_group_desc_init
    ext4_check_descriptors
      ext4_get_group_desc
        ext4_error
          ext4_handle_error
            ext4_commit_super
              ext4_update_super
                if (!es->s_error_count)
                  mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);
		  --> Accessing Uninitialized Variables
timer_setup(&sbi->s_err_report, print_daily_error_info, 0);

Maybe above issue is just theoretical, as ext4_check_descriptors() didn't
judge 'gpd' which get from ext4_get_group_desc(), if access to error handle
ext4_get_group_desc() will return NULL, then will trigger null-ptr-deref in
ext4_check_descriptors().
However, from the perspective of pure code, it is better to initialize
resource that may need to be used first.

Signed-off-by: default avatarYe Bin <yebin10@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230119013711.86680-1-yebin@huaweicloud.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 0f7bfd6f

fs/ext4/super.c

+7 −12
Original line number Diff line number Diff line
@@ -4738,7 +4738,6 @@ static int ext4_group_desc_init(struct super_block *sb, 
	struct ext4_sb_info *sbi = EXT4_SB(sb);

	unsigned int db_count;

	ext4_fsblk_t block;

	int ret;

	int i;



	db_count = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
@@ -4778,8 +4777,7 @@ static int ext4_group_desc_init(struct super_block *sb, 
			ext4_msg(sb, KERN_ERR,

			       "can't read group descriptor %d", i);

			sbi->s_gdb_count = i;

			ret = PTR_ERR(bh);

			goto out;

			return PTR_ERR(bh);

		}

		rcu_read_lock();

		rcu_dereference(sbi->s_group_desc)[i] = bh;
@@ -4788,13 +4786,10 @@ static int ext4_group_desc_init(struct super_block *sb, 
	sbi->s_gdb_count = db_count;

	if (!ext4_check_descriptors(sb, logical_sb_block, first_not_zeroed)) {

		ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");

		ret = -EFSCORRUPTED;

		goto out;

		return -EFSCORRUPTED;

	}



	return 0;

out:

	ext4_group_desc_free(sbi);

	return ret;

}



static int ext4_load_and_init_journal(struct super_block *sb,
@@ -5220,14 +5215,14 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) 
	if (ext4_geometry_check(sb, es))

		goto failed_mount;



	err = ext4_group_desc_init(sb, es, logical_sb_block, &first_not_zeroed);

	if (err)

		goto failed_mount;



	timer_setup(&sbi->s_err_report, print_daily_error_info, 0);

	spin_lock_init(&sbi->s_error_lock);

	INIT_WORK(&sbi->s_error_work, flush_stashed_error_work);



	err = ext4_group_desc_init(sb, es, logical_sb_block, &first_not_zeroed);

	if (err)

		goto failed_mount3;



	/* Register extent status tree shrinker */

	if (ext4_es_register_shrinker(sbi))

		goto failed_mount3;