linux-kernel - Re: race in sysfs between sysfs_remove

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]

Date:	Mon, 4 Dec 2006 11:57:07 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
cc:	Maneesh Soni <maneesh@...ibm.com>, <gregkh@...e.com>,
	<linux-usb-devel@...ts.sourceforge.net>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: race in sysfs between sysfs_remove_file() and read()/write() #2

On Mon, 4 Dec 2006, Oliver Neukum wrote:

> > Also, Oliver, it looks like the latest version of your patch makes an 
> > unnecessary change to sysfs_remove_file().
> 
> Code like:
> 
> int d(int a, int b)
> {
> 	return a + b;
> }
> 
> int c(int a, int b)
> {
> 	return d(a, b);
> }
> 
> is a detrimental to correct understanding and thence coding.
> In fact reading sysfs source code is like jumping all around the kernel
> tree. Such changes made it readable by normal people. I have to
> understand which method I am coding on to do reasonable work. ;-)

I was referring to sysfs_remove_file(), not sysfs_open_file() -- I agree 
that getting rid of the check_perm() routine is good.  But this isn't:

>  void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
>  {
> -       sysfs_hash_and_remove(kobj->dentry,attr->name);
> +       struct dentry *d = kobj->dentry;
> +
> +       sysfs_hash_and_remove(d, attr->name);
>  }

There's no apparent advantage to introducing the local variable d, either 
in terms of execution speed or readability.  (Although the original source 
line should have a space after the comma.)

Alan Stern

-
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/