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Miller" , Jakub Kicinski , Alexei Starovoitov , "Daniel Borkmann" , Alexey Kuznetsov , Hideaki YOSHIFUJI , Eric Dumazet CC: "linux-crypto@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "bpf@vger.kernel.org" , "netfilter-devel@vger.kernel.org" , "coreteam@netfilter.org" , "linux-sctp@vger.kernel.org" , "linux-hams@vger.kernel.org" , "linux-bluetooth@vger.kernel.org" , "bridge@lists.linux-foundation.org" , "linux-can@vger.kernel.org" , "dccp@vger.kernel.org" , "linux-decnet-user@lists.sourceforge.net" , "linux-wpan@vger.kernel.org" , "linux-s390@vger.kernel.org" , "mptcp@lists.01.org" , "lvs-devel@vger.kernel.org" , "rds-devel@oss.oracle.com" , "linux-afs@lists.infradead.org" , "tipc-discussion@lists.sourceforge.net" , "linux-x25@vger.kernel.org" Subject: RE: [PATCH 03/26] bpfilter: reject kernel addresses Thread-Topic: [PATCH 03/26] bpfilter: reject kernel addresses Thread-Index: AQHWYLhxJPyZOJNDGEen8+LVytPg86kVPIvA Date: Thu, 23 Jul 2020 14:42:11 +0000 Message-ID: References: <20200723060908.50081-1-hch@lst.de> <20200723060908.50081-4-hch@lst.de> In-Reply-To: <20200723060908.50081-4-hch@lst.de> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Christoph Hellwig > Sent: 23 July 2020 07:09 > > The bpfilter user mode helper processes the optval address using > process_vm_readv. Don't send it kernel addresses fed under > set_fs(KERNEL_DS) as that won't work. What sort of operations is the bpf filter doing on the sockopt buffers? Any attempts to reject some requests can be thwarted by a second application thread modifying the buffer after the bpf filter has checked that it allowed. You can't do security by reading a user buffer twice. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)