From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Date: Mon, 20 Jul 2020 17:55:43 +0000 Subject: Re: [PATCH 03/24] net: add a new sockptr_t type Message-Id: <20200720175543.GF1292162@gmail.com> List-Id: References: <20200720124737.118617-1-hch@lst.de> <20200720124737.118617-4-hch@lst.de> <20200720163748.GA1292162@gmail.com> <20200720174322.GA21785@lst.de> In-Reply-To: <20200720174322.GA21785@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Hellwig Cc: "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Alexey Kuznetsov , Hideaki YOSHIFUJI , Eric Dumazet , 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 On Mon, Jul 20, 2020 at 07:43:22PM +0200, Christoph Hellwig wrote: > On Mon, Jul 20, 2020 at 09:37:48AM -0700, Eric Biggers wrote: > > How does this not introduce a massive security hole when > > CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE? > > > > AFAICS, userspace can pass in a pointer >= TASK_SIZE, > > and this code makes it be treated as a kernel pointer. > > Yeah, we'll need to validate that before initializing the pointer. > > But thinking this a little further: doesn't this mean any > set_fs(KERNEL_DS) that has other user pointers than the one it is > intended for has the same issue? Pretty much all of these are gone > in mainline now, but in older stable kernels there might be some > interesting cases, especially in the compat ioctl handlers. Yes. I thought that eliminating that class of bug is one of the main motivations for your "remove set_fs" work. See commit 128394eff343 ("sg_write()/bsg_write() is not fit to be called under KERNEL_DS") for a case where this type of bug was fixed. Are you aware of any specific cases that weren't already fixed? If there are any, they need to be urgently fixed. - Eric