From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Laight Date: Thu, 23 Jul 2020 14:42:11 +0000 Subject: RE: [PATCH 03/26] bpfilter: reject kernel addresses Message-Id: List-Id: References: <20200723060908.50081-4-hch@lst.de> In-Reply-To: <20200723060908.50081-4-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: dccp@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)