linux-kernel - Re: [PATCH] block: fix double-free in the failure path of cgwb_bdi

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] [day] [month] [year] [list]

Message-ID: <66bc2094-3f13-91da-41c2-78fa1e8a81e8@fb.com>
Date:   Wed, 8 Feb 2017 13:52:52 -0700
From:   Jens Axboe <axboe@...com>
To:     Tejun Heo <tj@...nel.org>, Dmitry Vyukov <dvyukov@...gle.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>, <xiakaixu@...wei.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Joe Perches <joe@...ches.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH] block: fix double-free in the failure path of
 cgwb_bdi_init()

On 02/08/2017 01:19 PM, Tejun Heo wrote:
> When !CONFIG_CGROUP_WRITEBACK, bdi has single bdi_writeback_congested
> at bdi->wb_congested.  cgwb_bdi_init() allocates it with kzalloc() and
> doesn't do further initialization.  This usually works fine as the
> reference count gets bumped to 1 by wb_init() and the put from
> wb_exit() releases it.
> 
> However, when wb_init() fails, it puts the wb base ref automatically
> freeing the wb and the explicit kfree() in cgwb_bdi_init() error path
> ends up trying to free the same pointer the second time causing a
> double-free.
> 
> Fix it by explicitly initilizing the refcnt to 1 and putting the base
> ref from cgwb_bdi_destroy().

Queued up for 4.11.

-- 
Jens Axboe