Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933233AbbGHH5L (ORCPT ); Wed, 8 Jul 2015 03:57:11 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:43310 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933960AbbGHHgw (ORCPT ); Wed, 8 Jul 2015 03:36:52 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Willem de Bruijn , "David S. Miller" Subject: [PATCH 4.1 08/56] packet: avoid out of bounds read in round robin fanout Date: Wed, 8 Jul 2015 00:34:57 -0700 Message-Id: <20150708073238.228708993@linuxfoundation.org> X-Mailer: git-send-email 2.4.5 In-Reply-To: <20150708073237.780280770@linuxfoundation.org> References: <20150708073237.780280770@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2073 Lines: 68 4.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Willem de Bruijn [ Upstream commit 468479e6043c84f5a65299cc07cb08a22a28c2b1 ] PACKET_FANOUT_LB computes f->rr_cur such that it is modulo f->num_members. It returns the old value unconditionally, but f->num_members may have changed since the last store. Ensure that the return value is always < num. When modifying the logic, simplify it further by replacing the loop with an unconditional atomic increment. Fixes: dc99f600698d ("packet: Add fanout support.") Suggested-by: Eric Dumazet Signed-off-by: Willem de Bruijn Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/packet/af_packet.c | 18 ++---------------- 1 file changed, 2 insertions(+), 16 deletions(-) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1272,16 +1272,6 @@ static void packet_sock_destruct(struct sk_refcnt_debug_dec(sk); } -static int fanout_rr_next(struct packet_fanout *f, unsigned int num) -{ - int x = atomic_read(&f->rr_cur) + 1; - - if (x >= num) - x = 0; - - return x; -} - static unsigned int fanout_demux_hash(struct packet_fanout *f, struct sk_buff *skb, unsigned int num) @@ -1293,13 +1283,9 @@ static unsigned int fanout_demux_lb(stru struct sk_buff *skb, unsigned int num) { - int cur, old; + unsigned int val = atomic_inc_return(&f->rr_cur); - cur = atomic_read(&f->rr_cur); - while ((old = atomic_cmpxchg(&f->rr_cur, cur, - fanout_rr_next(f, num))) != cur) - cur = old; - return cur; + return val % num; } static unsigned int fanout_demux_cpu(struct packet_fanout *f, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/