nl_add_rtattr() unconditionally does memcpy(RTA_DATA(rta), data, len).
For zero-length attributes the callers pass data == NULL and len == 0,
for example the RTA_PREFSRC attribute added for proxy MFC entries:
if (mfc_attr->proxy)
rta = nl_add_rtattr(nlmsg, rta, RTA_PREFSRC, NULL, 0);
Passing a NULL pointer to memcpy() is undefined behaviour even when the
length is zero, because its source parameter is marked
__attribute__((nonnull)); it is flagged by fortify/-Wnonnull.
Only call memcpy() when len is non-zero.
Fixes: 05068eaa67b2 ("selftest: net: Add basic functionality tests for ipmr.")
Signed-off-by: Chaithanya Lagisetty <[email protected]>
---
tools/testing/selftests/net/forwarding/ipmr.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/net/forwarding/ipmr.c
b/tools/testing/selftests/net/forwarding/ipmr.c
index 9cd9f70de132..d3e26341821c 100644
--- a/tools/testing/selftests/net/forwarding/ipmr.c
+++ b/tools/testing/selftests/net/forwarding/ipmr.c
@@ -120,7 +120,8 @@ static struct rtattr *nl_add_rtattr(struct nlmsghdr *nlmsg,
struct rtattr *rta,
rta->rta_type = type;
rta->rta_len = RTA_LENGTH(len);
- memcpy(RTA_DATA(rta), data, len);
+ if (len)
+ memcpy(RTA_DATA(rta), data, len);
nlmsg->nlmsg_len += NLMSG_ALIGN(rta->rta_len);
--
2.43.0
