linux-kernel - Re: [PATCH 2/5] KEYS: user_defined: sanitize key payloads

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: <20170421183445.GB12755@gmail.com>
Date:   Fri, 21 Apr 2017 11:34:45 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     David Howells <dhowells@...hat.com>
Cc:     keyrings@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH 2/5] KEYS: user_defined: sanitize key payloads

On Fri, Apr 21, 2017 at 02:57:17PM +0100, David Howells wrote:
> Eric Biggers <ebiggers3@...il.com> wrote:
> 
> > -		kfree_rcu(zap, rcu);
> > +		call_rcu(&zap->rcu, user_free_payload_rcu);
> 
> Add kzfree_rcu()?
> 
> David

We could, but it's not trivial because the way kfree_rcu() works is to store the
offset of the rcu_head as the callback function, then have a special case in RCU
reclaim that recognizes "function pointers" with value < 4096 and call kfree()
rather than the function.  To support kzfree_rcu() we'd need to reserve another
4096 bytes of the address space (maybe at the end?), then check for the special
kzfree value on every RCU reclaim.  Or equivalently it could be a flag.  It's
possible, but it may be best to just use a custom callback for now.  Then if it
can be shown later that there are a lot of users who would like a
"kzfree_rcu()", it can be added.

- Eric