linux-kernel - Re: Problem with debugfs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-id: <20100925011800.GA6073@localhost>
Date:	Sat, 25 Sep 2010 09:18:00 +0800
From:	Kenneth <liguozhu@...wei.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: Problem with debugfs

Hi, all,

Yes, the problem is from code review, rather than in practice. I just wrote a
doc to introduce debugfs, and then I could not find a way to protect the
variable:)

I think add a comment to the header file will be good enough for this.

-- Kenneth


On Tue, Sep 21, 2010 at 02:13:10PM +0800, Kenneth wrote:
> Hello, Mr. Greg,
> 
> I'm sorry I had not checked the git before sending my last mail.
> 
> For the problem I mention, consider this scenarios:
> 
> 1. mm/hwpoinson-inject.c create a debugfs file with
>    debugfs_create_u64("corrupt-filter-flags-mask", ...,
>    &hwpoison_filter_flags_mask)
> 2. hwpoison_filter_flags_mask is supposed to be protected by filp->priv->mutex
>    of this file when it is accessed from user space.
> 3. but when it is accessed from mm/memory-failure.c:hwpoison_filter_flags,
>    there is no way for the function to protect the operation (so it simply
>    ignore it). This may create a competition problem.
> 
> It should be a problem.
> 
> I'm sorry from my poor English skill.
> 
> Best Regards
> Kenneth Lee
> 
> On Tue, Sep 21, 2010 at 10:21:12AM +0800, kenny wrote:
> > Hi, there,
> > 
> > I do not know who is the maintainer for debugfs now. But I think there is
> > problem with its API: It uses filp->priv->mutex to protect the read/write (to
> > the file) for the value of its attribute, but the mutex is not exported to the
> > API user.  Therefore, there is no way to protect its value when you directly
> > use the value in your module.
> > 
> > Is my understanding correct?
> > 
> > Thanks
> > 
> > 
> > Best Regards
> > Kenneth Lee
> 
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/