From: Matthew Wilcox <willy@infradead.org>
To: bsauce <bsauce00@gmail.com>
Cc: alexander.h.duyck@intel.com, vbabka@suse.cz, mgorman@suse.de,
l.stach@pengutronix.de, vdavydov.dev@gmail.com,
akpm@linux-foundation.org, alex@ghiti.fr, adobriyan@gmail.com,
mike.kravetz@oracle.com, rientjes@google.com,
rppt@linux.vnet.ibm.com, mhocko@suse.com, ksspiers@google.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fs/seq_file.c: Fix a UAF vulnerability in seq_release()
Date: Wed, 10 Jul 2019 05:25:49 -0700 [thread overview]
Message-ID: <20190710122549.GM32320@bombadil.infradead.org> (raw)
In-Reply-To: <1562754389-29217-1-git-send-email-bsauce00@gmail.com>
On Wed, Jul 10, 2019 at 06:26:29PM +0800, bsauce wrote:
> In seq_release(), 'm->buf' points to a chunk. It is freed but not cleared to null right away. It can be reused by seq_read() or srm_env_proc_write().
Well, no. The ->release method is called when there are no more file
descriptors referring to this file. So there's no way to call seq_read()
or srm_env_proc_write() after seq_release() is called.
> For example, /arch/alpha/kernel/srm_env.c provide several interfaces to userspace, like 'single_release', 'seq_read' and 'srm_env_proc_write'.
> Thus in userspace, one can exploit this UAF vulnerability to escape privilege.
Please provide a PoC.
next prev parent reply other threads:[~2019-07-10 12:26 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-10 10:26 bsauce
2019-07-10 10:58 ` Eric Dumazet
2019-07-10 12:25 ` Matthew Wilcox [this message]
2019-07-10 15:01 ` Alexander Duyck
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