[PATCH AUTOSEL 4.14 105/108] selftests/net: in timestamping, strncpy needs to preserve null byte

Sasha Levin
2020-06-18T01:47:22Z

From: tannerlove <tannerlove@google.com>

[ Upstream commit 8027bc0307ce59759b90679fa5d8b22949586d20 ]

If user passed an interface option longer than 15 characters, then
device.ifr_name and hwtstamp.ifr_name became non-null-terminated
strings. The compiler warned about this:

timestamping.c:353:2: warning: ‘strncpy’ specified bound 16 equals \
destination size [-Wstringop-truncation]
353 | strncpy(device.ifr_name, interface, sizeof(device.ifr_name));

Fixes: cb9eff097831 ("net: new user space API for time stamping of incoming and outgoing packets")
Signed-off-by: Tanner Love <tannerlove@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../selftests/networking/timestamping/timestamping.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/networking/timestamping/timestamping.c b/tools/testing/selftests/networking/timestamping/timestamping.c
index 5cdfd743447b..900ed4b47899 100644
--- a/tools/testing/selftests/networking/timestamping/timestamping.c
+++ b/tools/testing/selftests/networking/timestamping/timestamping.c
@@ -332,10 +332,16 @@ int main(int argc, char **argv)
int val;
socklen_t len;
struct timeval next;
+ size_t if_len;

if (argc < 2)
usage(0);
interface = argv[1];
+ if_len = strlen(interface);
+ if (if_len >= IFNAMSIZ) {
+ printf("interface name exceeds IFNAMSIZ\n");
+ exit(1);
+ }

for (i = 2; i < argc; i++) {
if (!strcasecmp(argv[i], "SO_TIMESTAMP"))
@@ -369,12 +375,12 @@ int main(int argc, char **argv)
bail("socket");

memset(&device, 0, sizeof(device));
- strncpy(device.ifr_name, interface, sizeof(device.ifr_name));
+ memcpy(device.ifr_name, interface, if_len + 1);
if (ioctl(sock, SIOCGIFADDR, &device) < 0)
bail("getting interface IP address");

memset(&hwtstamp, 0, sizeof(hwtstamp));
- strncpy(hwtstamp.ifr_name, interface, sizeof(hwtstamp.ifr_name));
+ memcpy(hwtstamp.ifr_name, interface, if_len + 1);
hwtstamp.ifr_data = (void *)&hwconfig;
memset(&hwconfig, 0, sizeof(hwconfig));
hwconfig.tx_type =
--
2.25.1