linux-kernel - Re: [PATCH] module: ban '.', '..' as module names, ban '/' in module names

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Message-ID: <Zh1menJ5GYy2ayFx@gallifrey>
Date: Mon, 15 Apr 2024 17:40:10 +0000
From: "Dr. David Alan Gilbert" <dave@...blig.org>
To: Alexey Dobriyan <adobriyan@...il.com>
Cc: Luis Chamberlain <mcgrof@...nel.org>, akpm@...ux-foundation.org,
	linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
	brauner@...nel.org, jack@...e.cz
Subject: Re: [PATCH] module: ban '.', '..' as module names, ban '/' in module
 names

* Alexey Dobriyan (adobriyan@...il.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@...ek:/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   |_______/