[PATCH 5.2 16/37] batman-adv: fix uninit-value in batadv_netlink_get_ifindex()

Greg Kroah-Hartman
2019-09-13T13:23:33Z

From: Eric Dumazet <edumazet@google.com>

commit 3ee1bb7aae97324ec9078da1f00cb2176919563f upstream.

batadv_netlink_get_ifindex() needs to make sure user passed
a correct u32 attribute.

syzbot reported :
BUG: KMSAN: uninit-value in batadv_netlink_dump_hardif+0x70d/0x880 net/batman-adv/netlink.c:968
CPU: 1 PID: 11705 Comm: syz-executor888 Not tainted 5.1.0+ #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x191/0x1f0 lib/dump_stack.c:113
kmsan_report+0x130/0x2a0 mm/kmsan/kmsan.c:622
__msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:310
batadv_netlink_dump_hardif+0x70d/0x880 net/batman-adv/netlink.c:968
genl_lock_dumpit+0xc6/0x130 net/netlink/genetlink.c:482
netlink_dump+0xa84/0x1ab0 net/netlink/af_netlink.c:2253
__netlink_dump_start+0xa3a/0xb30 net/netlink/af_netlink.c:2361
genl_family_rcv_msg net/netlink/genetlink.c:550 [inline]
genl_rcv_msg+0xfc1/0x1a40 net/netlink/genetlink.c:627
netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2486
genl_rcv+0x63/0x80 net/netlink/genetlink.c:638
netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
netlink_unicast+0xf3e/0x1020 net/netlink/af_netlink.c:1337
netlink_sendmsg+0x127e/0x12f0 net/netlink/af_netlink.c:1926
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:661 [inline]
___sys_sendmsg+0xcc6/0x1200 net/socket.c:2260
__sys_sendmsg net/socket.c:2298 [inline]
__do_sys_sendmsg net/socket.c:2307 [inline]
__se_sys_sendmsg+0x305/0x460 net/socket.c:2305
__x64_sys_sendmsg+0x4a/0x70 net/socket.c:2305
do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x440209

Fixes: b60620cf567b ("batman-adv: netlink: hardif query")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/batman-adv/netlink.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/batman-adv/netlink.c
+++ b/net/batman-adv/netlink.c
@@ -164,7 +164,7 @@ batadv_netlink_get_ifindex(const struct
{
struct nlattr *attr = nlmsg_find_attr(nlh, GENL_HDRLEN, attrtype);

- return attr ? nla_get_u32(attr) : 0;
+ return (attr && nla_len(attr) == sizeof(u32)) ? nla_get_u32(attr) : 0;
}

/**