From: Alexander Popov <alex.popov@linux.com>
To: zerons <zeronsaxm@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>,
kernel-hardening@lists.openwall.com,
Shawn <citypw@hardenedlinux.org>,
spender@grsecurity.net, Jann Horn <jannh@google.com>,
Kees Cook <keescook@chromium.org>
Subject: Re: Maybe inappropriate use BUG_ON() in CONFIG_SLAB_FREELIST_HARDENED
Date: Thu, 27 Feb 2020 14:28:30 +0300 [thread overview]
Message-ID: <04e89784-5ca8-0ecc-2735-4196ace74b0b@linux.com> (raw)
In-Reply-To: <68e01bc3-f218-01a1-2398-ec51ffa11109@gmail.com>
On 19.02.2020 16:43, zerons wrote:
> This patch does work for cve-2017-2636 case, it is barely impossible to win the
> race. My concern is based on an assumption: we do have a double kfree() bug and
> we can win the race.
Yes, I agree that the double-free check in CONFIG_SLAB_FREELIST_HARDENED can be
bypassed in some cases by winning the race and inserting kmalloc() between kfree().
But I *don't* agree that this double-free check can help the attacker.
Without this check in CONFIG_SLAB_FREELIST_HARDENED, double-free exploitation is
always easier, since the attacker has no need to race at all. In the write-up
about CVE-2017-2636 exploit [1] I showed how to do heap spray *after*
double-free (kfree-kfree-kmalloc-kmalloc).
Best regards,
Alexander
[1]: https://a13xp0p0v.github.io/2017/03/24/CVE-2017-2636.html
next prev parent reply other threads:[~2020-02-27 11:28 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 15:16 Maybe inappropriate use BUG_ON() in CONFIG_SLAB_FREELIST_HARDENED zerons
2020-02-17 15:15 ` Andrey Konovalov
2020-02-17 18:23 ` Kees Cook
2020-02-18 2:21 ` zerons
2020-02-18 20:54 ` Alexander Popov
2020-02-19 13:43 ` zerons
2020-02-27 11:28 ` Alexander Popov [this message]
2020-03-08 0:44 ` zerons
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