From 5e47868fb94b63c7068dcfd2469d99fba06bae9d Mon Sep 17 00:00:00 2001 From: Ritesh Harjani Date: Wed, 18 Mar 2020 11:43:01 +0530 Subject: [PATCH] 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 Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20200318061301.4320-1-riteshh@linux.ibm.com Signed-off-by: Theodore Ts'o --- fs/ext4/super.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 5dc65b7583cb..27ab130a40d1 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); -- 2.20.1