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>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 5dc65b7..27ab130 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -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);