> -原始邮件-
> 发件人: "Jan Kara"
> 发送时间: 2021-03-29 21:57:40 (星期一)
> 收件人: lyl2...@mail.ustc.edu.cn
> 抄送: j...@suse.cz, amir7...@gmail.com, linux-fsde...@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, lyl2...@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
> SUSE Labs, CR
Ok, thanks for your answer.
