netdev - [PATCH net 5/8] net: fix uninit-value in __hw_addr_add

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Message-Id: <20180407204243.176626-6-edumazet@google.com>
Date:   Sat,  7 Apr 2018 13:42:40 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net 5/8] net: fix uninit-value in __hw_addr_add_ex()

syzbot complained :

BUG: KMSAN: uninit-value in memcmp+0x119/0x180 lib/string.c:861
CPU: 0 PID: 3 Comm: kworker/0:0 Not tainted 4.16.0+ #82
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:53
 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
 memcmp+0x119/0x180 lib/string.c:861
 __hw_addr_add_ex net/core/dev_addr_lists.c:60 [inline]
 __dev_mc_add+0x1c2/0x8e0 net/core/dev_addr_lists.c:670
 dev_mc_add+0x6d/0x80 net/core/dev_addr_lists.c:687
 igmp6_group_added+0x2db/0xa00 net/ipv6/mcast.c:662
 ipv6_dev_mc_inc+0xe9e/0x1130 net/ipv6/mcast.c:914
 addrconf_join_solict net/ipv6/addrconf.c:2078 [inline]
 addrconf_dad_begin net/ipv6/addrconf.c:3828 [inline]
 addrconf_dad_work+0x427/0x2150 net/ipv6/addrconf.c:3954
 process_one_work+0x12c6/0x1f60 kernel/workqueue.c:2113
 worker_thread+0x113c/0x24f0 kernel/workqueue.c:2247
 kthread+0x539/0x720 kernel/kthread.c:239

Fixes: f001fde5eadd ("net: introduce a list of device addresses dev_addr_list (v6)")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
---
 net/core/dev_addr_lists.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/dev_addr_lists.c b/net/core/dev_addr_lists.c
index c0548d268e1a2ffa381082324cd5497c1fd49ffb..e3e6a3e2ca22a6ee634894e897b089773c820a9c 100644
--- a/net/core/dev_addr_lists.c
+++ b/net/core/dev_addr_lists.c
@@ -57,8 +57,8 @@ static int __hw_addr_add_ex(struct netdev_hw_addr_list *list,
 		return -EINVAL;
 
 	list_for_each_entry(ha, &list->list, list) {
-		if (!memcmp(ha->addr, addr, addr_len) &&
-		    ha->type == addr_type) {
+		if (ha->type == addr_type &&
+		    !memcmp(ha->addr, addr, addr_len)) {
 			if (global) {
 				/* check if addr is already used as global */
 				if (ha->global_use)
-- 
2.17.0.484.g0c8726318c-goog