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Date: Mon, 20 Jul 2020 10:55:43 -0700 From: Eric Biggers <ebiggers@...nel.org> To: Christoph Hellwig <hch@....de> Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, Eric Dumazet <edumazet@...gle.com>, linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, bpf@...r.kernel.org, netfilter-devel@...r.kernel.org, coreteam@...filter.org, linux-sctp@...r.kernel.org, linux-hams@...r.kernel.org, linux-bluetooth@...r.kernel.org, bridge@...ts.linux-foundation.org, linux-can@...r.kernel.org, dccp@...r.kernel.org, linux-decnet-user@...ts.sourceforge.net, linux-wpan@...r.kernel.org, linux-s390@...r.kernel.org, mptcp@...ts.01.org, lvs-devel@...r.kernel.org, rds-devel@....oracle.com, linux-afs@...ts.infradead.org, tipc-discussion@...ts.sourceforge.net, linux-x25@...r.kernel.org Subject: Re: [PATCH 03/24] net: add a new sockptr_t type 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
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