linux-kernel - [PATCH] ext4: fix memory leak in ext4_fill

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Date:   Wed, 28 Apr 2021 20:28:28 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     tytso@....edu, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        syzbot+d9e482e303930fa4f6ff@...kaller.appspotmail.com
Subject: [PATCH] ext4: fix memory leak in ext4_fill_super

syzbot reported memory leak in ext4 subsyetem.
The problem appears, when thread_stop() call happens
before wake_up_process().

Normally, this data will be freed by
created thread, but if kthread_stop()
returned -EINTR, this data should be freed manually

Reported-by: syzbot+d9e482e303930fa4f6ff@...kaller.appspotmail.com
Tested-by: syzbot+d9e482e303930fa4f6ff@...kaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---
 fs/ext4/super.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b9693680463a..9c33e97bd5c5 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5156,8 +5156,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 failed_mount3:
 	flush_work(&sbi->s_error_work);
 	del_timer_sync(&sbi->s_err_report);
-	if (sbi->s_mmp_tsk)
-		kthread_stop(sbi->s_mmp_tsk);
+	if (sbi->s_mmp_tsk) {
+		if (kthread_stop(sbi->s_mmp_tsk) == -EINTR)
+			kfree(kthread_data(sbi->s_mmp_tsk));
+	}
 failed_mount2:
 	rcu_read_lock();
 	group_desc = rcu_dereference(sbi->s_group_desc);
-- 
2.31.1