[PATCH 5.0 60/89] tipc: check link name with right length in tipc_nl_compat_link_set

[Greg Kroah-Hartman]

From: Xin Long <lucien....@gmail.com>

commit 8c63bf9ab4be8b83bd8c34aacfd2f1d2c8901c8a upstream.

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: syzbot+de00a87b8644a582a...@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien....@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 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
@@ -777,7 +777,12 @@ static int tipc_nl_compat_link_set(struc
 
        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;