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ext4: unregister sysfs path before destroying jbd2 journal 

Call ext4_unregister_sysfs(), before destroying jbd2 journal,
since below might cause, NULL pointer dereference issue.
This got reported with LTP tests.

ext4_put_super() 		cat /sys/fs/ext4/loop2/journal_task
	| 				ext4_attr_show();
ext4_jbd2_journal_destroy();  			|
    	|				 journal_task_show()
	| 					|
	| 				task_pid_vnr(NULL);
sbi->s_journal = NULL;

Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200318061301.4320-1-riteshh@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Ritesh Harjani 2020-03-18 11:43:01 +05:30 committed by Theodore Ts'o
parent f1eec3b0d0
commit 5e47868fb9
1 changed files with 7 additions and 1 deletions
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8
fs/ext4/super.c
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@ -1024,6 +1024,13 @@ static void ext4_put_super(struct super_block *sb)
destroy_workqueue(sbi->rsv_conversion_wq);
/*
* Unregister sysfs before destroying jbd2 journal.
* Since we could still access attr_journal_task attribute via sysfs
* path which could have sbi->s_journal->j_task as NULL
*/
ext4_unregister_sysfs(sb);
if (sbi->s_journal) {
aborted = is_journal_aborted(sbi->s_journal);
err = jbd2_journal_destroy(sbi->s_journal);
@ -1034,7 +1041,6 @@ static void ext4_put_super(struct super_block *sb)
}
}
ext4_unregister_sysfs(sb);
ext4_es_unregister_shrinker(sbi);
del_timer_sync(&sbi->s_err_report);
ext4_release_system_zone(sb);