[tipc-discussion] [PATCH net 2/3] tipc: check link name with right length in tipc_nl_compat_link_set

[Xin L. <luc...@gm...>]

A similar issue as fixed by Patch "tipc: check bearer name with right
length in tipc_nl_compat_bearer_enable" was also found by syzbot in
tipc_nl_compat_link_set().

The length to check with should be 'TLV_GET_DATA_LEN(msg->req) -
offsetof(struct tipc_link_config, name)'.

Reported-by: syz...@sy...
Signed-off-by: Xin Long <luc...@gm...>
---
 net/tipc/netlink_compat.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c
index 5f8e53c..0bfd03d6 100644
--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -771,7 +771,12 @@ static int tipc_nl_compat_link_set(struct tipc_nl_compat_cmd_doit *cmd,
 
 	lc = (struct tipc_link_config *)TLV_DATA(msg->req);
 
-	len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_LINK_NAME);
+	len = TLV_GET_DATA_LEN(msg->req);
+	len -= offsetof(struct tipc_link_config, name);
+	if (len <= 0)
+		return -EINVAL;
+
+	len = min_t(int, len, TIPC_MAX_LINK_NAME);
 	if (!string_is_valid(lc->name, len))
 		return -EINVAL;
 
-- 
2.1.0