Received-SPF: pass (google.com: domain of linux-kernel+bounces-145683-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Mon, 15 Apr 2024 17:40:10 +0000
From: "Dr. David Alan Gilbert" <dave@treblig.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>, akpm@linux-foundation.org,
	linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk,
	brauner@kernel.org, jack@suse.cz
Subject: Re: [PATCH] module: ban '.', '..' as module names, ban '/' in module
 names
Message-ID: <Zh1menJ5GYy2ayFx@gallifrey>
References: <ee371cf7-69fa-4f9c-99b9-59bab86f25e4@p183>
 <ZhxDj3vQFLy62Yow@bombadil.infradead.org>
 <e770923a-6719-403c-a9f2-1f7ac4313474@p183>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <e770923a-6719-403c-a9f2-1f7ac4313474@p183>
User-Agent: Mutt/2.2.12 (2023-09-09)

* Alexey Dobriyan (adobriyan@gmail.com) wrote:
> On Sun, Apr 14, 2024 at 01:58:55PM -0700, Luis Chamberlain wrote:
> > On Sun, Apr 14, 2024 at 10:05:05PM +0300, Alexey Dobriyan wrote:
> > > --- a/include/linux/fs.h
> > > +++ b/include/linux/fs.h
> > > @@ -3616,4 +3616,12 @@ extern int vfs_fadvise(struct file *file, loff_t offset, loff_t len,
> > >  extern int generic_fadvise(struct file *file, loff_t offset, loff_t len,
> > >  			   int advice);
> > >  
> > > +/*
> > > + * Use this if data from userspace end up as directory/filename on
> > > + * some virtual filesystem.
> > > + */
> > > +static inline bool string_is_vfs_ready(const char *s)
> > > +{
> > > +	return strcmp(s, ".") != 0 && strcmp(s, "..") != 0 && !strchr(s, '/');
> > > +}
> > >  #endif /* _LINUX_FS_H */
> > > --- a/kernel/module/main.c
> > > +++ b/kernel/module/main.c
> > > @@ -2893,6 +2893,11 @@ static int load_module(struct load_info *info, const char __user *uargs,
> > >  
> > >  	audit_log_kern_module(mod->name);
> > >  
> > > +	if (!string_is_vfs_ready(mod->name)) {
> > > +		err = -EINVAL;
> > > +		goto free_module;
> > > +	}
> > > +
> > 
> > Sensible change however to put string_is_vfs_ready() in include/linux/fs.h 
> > is a stretch if there really are no other users.
> 
> This is forward thinking patch :-)
> 
> Other subsystems may create files/directories in proc/sysfs, and should
> check for bad names as well:
> 
> 	/proc/2821/net/dev_snmp6/eth0
> 
> This looks exactly like something coming from userspace and making it
> into /proc, so the filter function doesn't belong to kernel/module/internal.h

You mean like:

[24180.292204] tuxthe____: renamed from tuxthe????
root@dalek:/home/dg# ls /sys/class/net/
enp5s0  lo  tuxthe____  tuxthe????  tuxthe????  virbr0  virbr1

?

Dave
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/