From: lyl2019@mail.ustc.edu.cn
To: "Jan Kara" <jack@suse.cz>
Cc: amir73il@gmail.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: Re: [BUG] fs/notify/mark: A potential use after free in fsnotify_put_mark_wake
Date: Mon, 29 Mar 2021 22:07:52 +0800 (GMT+08:00) [thread overview]
Message-ID: <560cb051.1d0ba.1787e4ff42a.Coremail.lyl2019@mail.ustc.edu.cn> (raw)
In-Reply-To: <20210329135740.GB4283@quack2.suse.cz>
> -----原始邮件-----
> 发件人: "Jan Kara" <jack@suse.cz>
> 发送时间: 2021-03-29 21:57:40 (星期一)
> 收件人: lyl2019@mail.ustc.edu.cn
> 抄送: jack@suse.cz, amir73il@gmail.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
> 主题: Re: [BUG] fs/notify/mark: A potential use after free in fsnotify_put_mark_wake
>
> Hello!
>
>
> On Sun 28-03-21 17:11:43, lyl2019@mail.ustc.edu.cn wrote:
> > My static analyzer tool reported a use after free in fsnotify_put_mark_wake
> > of the file: fs/notify/mark.c.
> >
> > In fsnotify_put_mark_wake, it calls fsnotify_put_mark(mark). Inside the function
> > fsnotify_put_mark(), if conn is NULL, it will call fsnotify_final_mark_destroy(mark)
> > to free mark->group by fsnotify_put_group(group) and return. I also had inspected
> > the implementation of fsnotify_put_group() and found that there is no cleanup operation
> > about group->user_waits.
> >
> > But after fsnotify_put_mark_wake() returned, mark->group is still used by
> > if (atomic_dec_and_test(&group->user_waits) && group->shutdown) and later.
> >
> > Is this an issue?
>
> I don't think this scenario is possible. fsnotify_put_mark_wake() can be
> called only for marks attached to objects and these have mark->conn !=
> NULL and we are sure that fsnotify_destroy_group() will wait for all such
> marks to be torn down and freed before dropping last group reference and
> freeing the group.
>
> Honza
> --
> Jan Kara <jack@suse.com>
> SUSE Labs, CR
Ok, thanks for your answer.
prev parent reply other threads:[~2021-03-29 14:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-28 9:11 [BUG] fs/notify/mark: A potential use after free in fsnotify_put_mark_wake lyl2019
2021-03-29 13:57 ` Jan Kara
2021-03-29 14:07 ` lyl2019 [this message]
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