From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Cline Subject: Re: [PATCH 2/2] net: socket: Fix potential spectre v1 gadget in sock_is_registered Date: Mon, 13 Aug 2018 20:03:20 +0100 Message-ID: References: <20180727224302.5503-1-jcline@redhat.com> <20180727224302.5503-3-jcline@redhat.com> <20180729135906.lgqo5ue6it3hl2da@treble> <914d34af-ba80-93b9-6f17-413eef8bf210@redhat.com> <20180813171642.wlxmnzgsg2rkwe4o@treble> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: "David S . Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org To: Josh Poimboeuf Return-path: In-Reply-To: <20180813171642.wlxmnzgsg2rkwe4o@treble> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 08/13/2018 06:16 PM, Josh Poimboeuf wrote: > On Sun, Jul 29, 2018 at 11:59:36AM -0400, Jeremy Cline wrote: >> On 07/29/2018 09:59 AM, Josh Poimboeuf wrote: >>> On Fri, Jul 27, 2018 at 10:43:02PM +0000, Jeremy Cline wrote: >>>> 'family' can be a user-controlled value, so sanitize it after the bounds >>>> check to avoid speculative out-of-bounds access. >>>> >>>> Cc: Josh Poimboeuf >>>> Cc: stable@vger.kernel.org >>>> Signed-off-by: Jeremy Cline >>>> --- >>>> net/socket.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/net/socket.c b/net/socket.c >>>> index f15d5cbb3ba4..608e29ae6baf 100644 >>>> --- a/net/socket.c >>>> +++ b/net/socket.c >>>> @@ -2672,7 +2672,8 @@ EXPORT_SYMBOL(sock_unregister); >>>> >>>> bool sock_is_registered(int family) >>>> { >>>> - return family < NPROTO && rcu_access_pointer(net_families[family]); >>>> + return family < NPROTO && >>>> + rcu_access_pointer(net_families[array_index_nospec(family, NPROTO)]); >>>> } >>>> >>>> static int __init sock_init(void) >>> >>> This is another one where I think it would be better to do the nospec >>> clamp higher up the call chain. The untrusted 'family' value comes from >>> __sock_diag_cmd(): >>> >>> __sock_diag_cmd >>> sock_load_diag_module >>> sock_is_registered >>> >>> That function has a bounds check, and also uses the value in some other >>> array accesses: >>> >>> if (req->sdiag_family >= AF_MAX) >>> return -EINVAL; >>> >>> if (sock_diag_handlers[req->sdiag_family] == NULL) >>> sock_load_diag_module(req->sdiag_family, 0); >>> >>> mutex_lock(&sock_diag_table_mutex); >>> hndl = sock_diag_handlers[req->sdiag_family]; >>> ... >>> >>> So I think clamping 'req->sdiag_family' right after the bounds check >>> would be the way to go. >>> >> >> Indeed, the clamp there would cover this clamp. I had a scheme that I >> quickly fix all the gadgets in functions with local comparisons, but >> clearly that's going to result in call chains with multiple clamps. >> >> I can fix this in a follow-up with a clamp here, or respin this patch >> set, whatever is easier for David. > > Hi Jeremy, > > Just checking up on this... since this patch was merged, will you be > doing a followup patch? > Yes, apologies, I've been traveling. I'll have a patch tomorrow.