linux-kernel - Re: [PATCH V9] devcoredump: add context check in dev

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

Message-ID: <66a140d1.f7b7e.1837884be23.Coremail.duoming@zju.edu.cn>
Date:   Mon, 26 Sep 2022 14:38:28 +0800 (GMT+08:00)
From:   duoming@....edu.cn
To:     "Greg KH" <gregkh@...uxfoundation.org>
Cc:     johannes@...solutions.net, linux-kernel@...r.kernel.org,
        rafael@...nel.org
Subject: Re: [PATCH V9] devcoredump: add context check in dev_coredumpm

Hello,

On Mon, 26 Sep 2022 08:27:58 +0200 Greg KH wrote:

> On Mon, Sep 26, 2022 at 02:16:09PM +0800, Duoming Zhou wrote:
> > The dev_coredumpm(), dev_coredumpv() and dev_coredumpsg() could not
> > be used in atomic context, because they call kvasprintf_const() and
> > kstrdup() with GFP_KERNEL parameter. The process is shown below:
> > 
> > dev_coredumpv(.., gfp_t gfp)
> >   dev_coredumpm(.., gfp_t gfp)
> >     dev_set_name
> >       kobject_set_name_vargs
> >         kvasprintf_const(GFP_KERNEL, ...); //may sleep
> >           kstrdup(s, GFP_KERNEL); //may sleep
> > 
> > This patch adds context check in dev_coredumpm() in order to show
> > dev_coredumpm() and its callers could not be used in atomic context.
> > 
> > What's more, this change can allow the api to evolve and will not
> > influence the users that call this api.
> > 
> > Fixes: 833c95456a70 ("device coredump: add new device coredump class")
> > Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> > ---
> > Changes in v9:
> >   - Add context check in dev_coredumpm().
> > 
> >  drivers/base/devcoredump.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c
> > index f4d794d6bb8..806ee872f5f 100644
> > --- a/drivers/base/devcoredump.c
> > +++ b/drivers/base/devcoredump.c
> > @@ -255,6 +255,9 @@ void dev_coredumpm(struct device *dev, struct module *owner,
> >  	struct devcd_entry *devcd;
> >  	struct device *existing;
> >  
> > +	if (!gfpflags_normal_context(gfp))
> > +		goto free;
> 
> Wait, this just broke things for no good reason if a caller happened to
> have set a GFP flag that we do not like at the moment.
> 
> What code now does not work that previously did work with this change?

I found that all users in the kernel call the dev_coredumpv(), dev_coredumpm() and
dev_coredumpsg() with "GFP_KERNEL". So this change will not influence the existing users.

Best regards,
Duoming Zhou