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Subject[PATCH 4.9 27/41] tipc: check bearer name with right length in tipc_nl_compat_bearer_enable
From: Xin Long <>

commit 6f07e5f06c8712acc423485f657799fc8e11e56c upstream.

Syzbot reported the following crash:

BUG: KMSAN: uninit-value in memchr+0xce/0x110 lib/string.c:961
memchr+0xce/0x110 lib/string.c:961
string_is_valid net/tipc/netlink_compat.c:176 [inline]
tipc_nl_compat_bearer_enable+0x2c4/0x910 net/tipc/netlink_compat.c:401
__tipc_nl_compat_doit net/tipc/netlink_compat.c:321 [inline]
tipc_nl_compat_doit+0x3aa/0xaf0 net/tipc/netlink_compat.c:354
tipc_nl_compat_handle net/tipc/netlink_compat.c:1162 [inline]
tipc_nl_compat_recv+0x1ae7/0x2750 net/tipc/netlink_compat.c:1265
genl_family_rcv_msg net/netlink/genetlink.c:601 [inline]
genl_rcv_msg+0x185f/0x1a60 net/netlink/genetlink.c:626
netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477
genl_rcv+0x63/0x80 net/netlink/genetlink.c:637
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0xf3e/0x1020 net/netlink/af_netlink.c:1336
netlink_sendmsg+0x127f/0x1300 net/netlink/af_netlink.c:1917
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg net/socket.c:632 [inline]

Uninit was created at:
__alloc_skb+0x309/0xa20 net/core/skbuff.c:208
alloc_skb include/linux/skbuff.h:1012 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
netlink_sendmsg+0xb82/0x1300 net/netlink/af_netlink.c:1892
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg net/socket.c:632 [inline]

It was triggered when the bearer name size < TIPC_MAX_BEARER_NAME,
it would check with a wrong len/TLV_GET_DATA_LEN(msg->req), which
also includes priority and disc_domain length.

This patch is to fix it by checking it with a right length:
'TLV_GET_DATA_LEN(msg->req) - offsetof(struct tipc_bearer_config, name)'.

Signed-off-by: Xin Long <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>

net/tipc/netlink_compat.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -394,7 +394,12 @@ static int tipc_nl_compat_bearer_enable(
if (!bearer)
return -EMSGSIZE;

- len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_BEARER_NAME);
+ len = TLV_GET_DATA_LEN(msg->req);
+ len -= offsetof(struct tipc_bearer_config, name);
+ if (len <= 0)
+ return -EINVAL;
+ len = min_t(int, len, TIPC_MAX_BEARER_NAME);
if (!string_is_valid(b->name, len))
return -EINVAL;

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