[PATCH 3.16 122/366] net: fix uninit-value in __hw_addr_add_ex()

Ben Hutchings
2018-10-14T15:25:41Z

From: Eric Dumazet <edumazet@google.com>

commit 77d36398d99f2565c0a8d43a86fd520a82e64bb8 upstream.

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@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/core/dev_addr_lists.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- 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 netde
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)