From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jason A. Donenfeld" Date: Tue, 28 Jul 2020 08:17:28 +0000 Subject: Re: [PATCH 12/26] netfilter: switch nf_setsockopt to sockptr_t Message-Id: List-Id: References: <20200723060908.50081-1-hch@lst.de> <20200723060908.50081-13-hch@lst.de> <20200727150310.GA1632472@zx2c4.com> <20200727150601.GA3447@lst.de> <20200727162357.GA8022@lst.de> <908ed73081cc42d58a5b01e0c97dbe47@AcuMS.aculab.com> In-Reply-To: <908ed73081cc42d58a5b01e0c97dbe47@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Laight Cc: Christoph Hellwig , "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Alexey Kuznetsov , Hideaki YOSHIFUJI , Eric Dumazet , Linux Crypto Mailing List , LKML , Netdev , "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" , Kernel Hardening On Tue, Jul 28, 2020 at 10:07 AM David Laight wrote: > > From: Christoph Hellwig > > Sent: 27 July 2020 17:24 > > > > On Mon, Jul 27, 2020 at 06:16:32PM +0200, Jason A. Donenfeld wrote: > > > Maybe sockptr_advance should have some safety checks and sometimes > > > return -EFAULT? Or you should always use the implementation where > > > being a kernel address is an explicit bit of sockptr_t, rather than > > > being implicit? > > > > I already have a patch to use access_ok to check the whole range in > > init_user_sockptr. > > That doesn't make (much) difference to the code paths that ignore > the user-supplied length. > OTOH doing the user/kernel check on the base address (not an > incremented one) means that the correct copy function is always > selected. Right, I had the same reaction in reading this, but actually, his code gets rid of the sockptr_advance stuff entirely and never mutates, so even though my point about attacking those pointers was missed, the code does the better thing now -- checking the base address and never mutating the pointer. So I think we're good. > > Perhaps the functions should all be passed a 'const sockptr_t'. > The typedef could be made 'const' - requiring non-const items > explicitly use the union/struct itself. I was thinking the same, but just by making the pointers inside the struct const. However, making the whole struct const via the typedef is a much better idea. That'd probably require changing the signature of init_user_sockptr a bit, which would be fine, but indeed I think this would be a very positive change. Jason