From: Pavel Skripkin <paskripkin@gmail.com>
To: tytso@mit.edu, adilger.kernel@dilger.ca
Cc: linux-ext4@vger.kernel.org, kernel list <linux-kernel@vger.kernel.org>
Subject: memory leak in ext4_multi_mount_protect
Date: Tue, 13 Apr 2021 16:11:41 +0300 [thread overview]
Message-ID: <d37a412f244eaa0f1352b394fdf933ce75d9968c.camel@gmail.com> (raw)
Hi!
I've done debugging on this issue
https://syzkaller.appspot.com/bug?id=420258a304e5d92cfef6b0097f87b42506e1db08
and I want to ask you about
proper way of fixing it. The problem was in case sbi->s_mmp_tsk hasn’t
started at the time of kthread_stop() call. In that case allocated data
won't be freed.
I wrote fix patch, but I am confused about it, because I didn't find
any kernel code like this. I don't think, that adding new members to
struct super_block is good idea, that's why I came to that decision:
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);
I look forward to hearing your perspective on this patch :)
With regards,
Pavel Skripkin
next reply other threads:[~2021-04-13 13:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 13:11 Pavel Skripkin [this message]
-- strict thread matches above, loose matches on Subject: below --
2020-12-24 9:55 memory leak in ext4_multi_mount_protect syzbot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d37a412f244eaa0f1352b394fdf933ce75d9968c.camel@gmail.com \
--to=paskripkin@gmail.com \
--cc=adilger.kernel@dilger.ca \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).