[PATCH 4.14 137/189] tipc: eliminate KMSAN uninit-value in strcmp complaint

Greg Kroah-Hartman
2018-06-18T08:37:00Z

From: Ying Xue <ying.xue@windriver.com>

[ Upstream commit 94f6a80c0c11828cb7b3d79294459dd8d761ca89 ]

When we get link properties through netlink interface with
tipc_nl_node_get_link(), we don't validate TIPC_NLA_LINK_NAME
attribute at all, instead we directly use it. As a consequence,
KMSAN detected the TIPC_NLA_LINK_NAME attribute was an uninitialized
value, and then posted the following complaint:

==================================================================
BUG: KMSAN: uninit-value in strcmp+0xf7/0x160 lib/string.c:329
CPU: 1 PID: 4527 Comm: syz-executor655 Not tainted 4.16.0+ #87
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
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:683
strcmp+0xf7/0x160 lib/string.c:329
tipc_nl_node_get_link+0x220/0x6f0 net/tipc/node.c:1881
genl_family_rcv_msg net/netlink/genetlink.c:599 [inline]
genl_rcv_msg+0x1686/0x1810 net/netlink/genetlink.c:624
netlink_rcv_skb+0x378/0x600 net/netlink/af_netlink.c:2447
genl_rcv+0x63/0x80 net/netlink/genetlink.c:635
netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
netlink_unicast+0x166b/0x1740 net/netlink/af_netlink.c:1337
netlink_sendmsg+0x1048/0x1310 net/netlink/af_netlink.c:1900
sock_sendmsg_nosec net/socket.c:630 [inline]
sock_sendmsg net/socket.c:640 [inline]
___sys_sendmsg+0xec0/0x1310 net/socket.c:2046
__sys_sendmsg net/socket.c:2080 [inline]
SYSC_sendmsg+0x2a3/0x3d0 net/socket.c:2091
SyS_sendmsg+0x54/0x80 net/socket.c:2087
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x445589
RSP: 002b:00007fb7ee66cdb8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006dac24 RCX: 0000000000445589
RDX: 0000000000000000 RSI: 0000000020023000 RDI: 0000000000000003
RBP: 00000000006dac20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fffa2bf3f3f R14: 00007fb7ee66d9c0 R15: 0000000000000001

Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
slab_post_alloc_hook mm/slab.h:445 [inline]
slab_alloc_node mm/slub.c:2737 [inline]
__kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
__kmalloc_reserve net/core/skbuff.c:138 [inline]
__alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
alloc_skb include/linux/skbuff.h:984 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1183 [inline]
netlink_sendmsg+0x9a6/0x1310 net/netlink/af_netlink.c:1875
sock_sendmsg_nosec net/socket.c:630 [inline]
sock_sendmsg net/socket.c:640 [inline]
___sys_sendmsg+0xec0/0x1310 net/socket.c:2046
__sys_sendmsg net/socket.c:2080 [inline]
SYSC_sendmsg+0x2a3/0x3d0 net/socket.c:2091
SyS_sendmsg+0x54/0x80 net/socket.c:2087
do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
==================================================================

To quiet the complaint, TIPC_NLA_LINK_NAME attribute has been
validated in tipc_nl_node_get_link() before it's used.

Reported-by: syzbot+df0257c92ffd4fcc58cd@syzkaller.appspotmail.com
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/tipc/node.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -1831,6 +1831,7 @@ out:
int tipc_nl_node_get_link(struct sk_buff *skb, struct genl_info *info)
{
struct net *net = genl_info_net(info);
+ struct nlattr *attrs[TIPC_NLA_LINK_MAX + 1];
struct tipc_nl_msg msg;
char *name;
int err;
@@ -1838,9 +1839,19 @@ int tipc_nl_node_get_link(struct sk_buff
msg.portid = info->snd_portid;
msg.seq = info->snd_seq;

- if (!info->attrs[TIPC_NLA_LINK_NAME])
+ if (!info->attrs[TIPC_NLA_LINK])
return -EINVAL;
- name = nla_data(info->attrs[TIPC_NLA_LINK_NAME]);
+
+ err = nla_parse_nested(attrs, TIPC_NLA_LINK_MAX,
+ info->attrs[TIPC_NLA_LINK],
+ tipc_nl_link_policy, info->extack);
+ if (err)
+ return err;
+
+ if (!attrs[TIPC_NLA_LINK_NAME])
+ return -EINVAL;
+
+ name = nla_data(attrs[TIPC_NLA_LINK_NAME]);

msg.skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
if (!msg.skb)