[PATCH bpf-next V2 4/4] selftests/bpf: xdp_hw_metadata use strncpy for ifname

[Jesper Dangaard Brouer <brouer@xxxxxxxxxx>]

The ifname char pointer is taken directly from the command line
as input and the string is copied directly into struct ifreq
via strcpy. This makes it easy to corrupt other members of ifreq
and generally do stack overflows.

Most often the ioctl will fail with:
 ./xdp_hw_metadata: ioctl(SIOCETHTOOL): Bad address

As people will likely copy-paste code for getting NIC queue
channels (rxq_num) and enabling HW timestamping (hwtstamp_ioctl)
lets make this code a bit more secure by using strncpy.

Fixes: 297a3f124155 ("selftests/bpf: Simple program to dump XDP RX metadata")
Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
---
 tools/testing/selftests/bpf/xdp_hw_metadata.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
index 58fde35abad7..2a66bd3f2c9f 100644
--- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
+++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
@@ -270,7 +270,7 @@ static int rxq_num(const char *ifname)
 	struct ifreq ifr = {
 		.ifr_data = (void *)&ch,
 	};
-	strcpy(ifr.ifr_name, ifname);
+	strncpy(ifr.ifr_name, ifname, IF_NAMESIZE - 1);
 	int fd, ret;
 
 	fd = socket(AF_UNIX, SOCK_DGRAM, 0);
@@ -291,7 +291,7 @@ static void hwtstamp_ioctl(int op, const char *ifname, struct hwtstamp_config *c
 	struct ifreq ifr = {
 		.ifr_data = (void *)cfg,
 	};
-	strcpy(ifr.ifr_name, ifname);
+	strncpy(ifr.ifr_name, ifname, IF_NAMESIZE - 1);
 	int fd, ret;
 
 	fd = socket(AF_UNIX, SOCK_DGRAM, 0);