[PATCH] net/tap: avoid memcpy with NULL arg

[Stephen Hemminger]

Calling memcpy with a null pointer even if zero length is
undefined, so check if data_length is zero.
Problem reported by Gcc analyzer.

Signed-off-by: Stephen Hemminger <step...@networkplumber.org>
---
 drivers/net/tap/tap_netlink.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tap/tap_netlink.c b/drivers/net/tap/tap_netlink.c
index c7db78563a..8a57c9242c 100644
--- a/drivers/net/tap/tap_netlink.c
+++ b/drivers/net/tap/tap_netlink.c
@@ -302,7 +302,8 @@ tap_nlattr_add(struct nlmsghdr *nh, unsigned short type,
        rta = (struct rtattr *)NLMSG_TAIL(nh);
        rta->rta_len = RTA_LENGTH(data_len);
        rta->rta_type = type;
-       memcpy(RTA_DATA(rta), data, data_len);
+       if (data_len > 0)
+               memcpy(RTA_DATA(rta), data, data_len);
        nh->nlmsg_len = NLMSG_ALIGN(nh->nlmsg_len) + RTA_ALIGN(rta->rta_len);
 }
 
-- 
2.43.0