Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932713AbbG1JtP (ORCPT ); Tue, 28 Jul 2015 05:49:15 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:37495 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755416AbbG1Jps (ORCPT ); Tue, 28 Jul 2015 05:45:48 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Willem de Bruijn , "David S. Miller" , Jiri Slaby Subject: [PATCH 3.12 082/124] packet: avoid out of bounds read in round robin fanout Date: Tue, 28 Jul 2015 11:43:36 +0200 Message-Id: X-Mailer: git-send-email 2.4.6 In-Reply-To: <90d8a5681e4a9e320611b422f0ed012e148c2bca.1438076484.git.jslaby@suse.cz> References: <90d8a5681e4a9e320611b422f0ed012e148c2bca.1438076484.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2189 Lines: 71 From: Willem de Bruijn 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ 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: Jiri Slaby --- net/packet/af_packet.c | 18 ++---------------- 1 file changed, 2 insertions(+), 16 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index e844c6152570..7f63613148b9 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1150,16 +1150,6 @@ static void packet_sock_destruct(struct sock *sk) 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) @@ -1171,13 +1161,9 @@ static unsigned int fanout_demux_lb(struct packet_fanout *f, 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, -- 2.4.6 -- 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/