selftests/bpf: fix -Wstrict-aliasing in test_sockopt_sk.c

Let's use union with u8[4] and u32 members for sockopt buffer,
that should fix any possible aliasing issues.

test_sockopt_sk.c: In function ‘getsetsockopt’:
test_sockopt_sk.c:115:2: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  if (*(__u32 *)buf != 0x55AA*2) {
  ^~
test_sockopt_sk.c:116:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
   log_err("Unexpected getsockopt(SO_SNDBUF) 0x%x != 0x55AA*2",
   ^~~~~~~

Fixes: 8a027dc0d8f5 ("selftests/bpf: add sockopt test that exercises sk helpers")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/testing/selftests/bpf/test_sockopt_sk.c b/tools/testing/selftests/bpf/test_sockopt_sk.c
index 12e79ed..036b652 100644 (file)
--- a/tools/testing/selftests/bpf/test_sockopt_sk.c
+++ b/tools/testing/selftests/bpf/test_sockopt_sk.c
@@ -22,7 +22,10 @@
 static int getsetsockopt(void)
 {
        int fd, err;
-       char buf[4] = {};
+       union {
+               char u8[4];
+               __u32 u32;
+       } buf = {};
        socklen_t optlen;
 
        fd = socket(AF_INET, SOCK_STREAM, 0);
@@ -33,31 +36,31 @@ static int getsetsockopt(void)
 
        /* IP_TOS - BPF bypass */
 
-       buf[0] = 0x08;
-       err = setsockopt(fd, SOL_IP, IP_TOS, buf, 1);
+       buf.u8[0] = 0x08;
+       err = setsockopt(fd, SOL_IP, IP_TOS, &buf, 1);
        if (err) {
                log_err("Failed to call setsockopt(IP_TOS)");
                goto err;
        }
 
-       buf[0] = 0x00;
+       buf.u8[0] = 0x00;
        optlen = 1;
-       err = getsockopt(fd, SOL_IP, IP_TOS, buf, &optlen);
+       err = getsockopt(fd, SOL_IP, IP_TOS, &buf, &optlen);
        if (err) {
                log_err("Failed to call getsockopt(IP_TOS)");
                goto err;
        }
 
-       if (buf[0] != 0x08) {
+       if (buf.u8[0] != 0x08) {
                log_err("Unexpected getsockopt(IP_TOS) buf[0] 0x%02x != 0x08",
-                       buf[0]);
+                       buf.u8[0]);
                goto err;
        }
 
        /* IP_TTL - EPERM */
 
-       buf[0] = 1;
-       err = setsockopt(fd, SOL_IP, IP_TTL, buf, 1);
+       buf.u8[0] = 1;
+       err = setsockopt(fd, SOL_IP, IP_TTL, &buf, 1);
        if (!err || errno != EPERM) {
                log_err("Unexpected success from setsockopt(IP_TTL)");
                goto err;
@@ -65,16 +68,16 @@ static int getsetsockopt(void)
 
        /* SOL_CUSTOM - handled by BPF */
 
-       buf[0] = 0x01;
-       err = setsockopt(fd, SOL_CUSTOM, 0, buf, 1);
+       buf.u8[0] = 0x01;
+       err = setsockopt(fd, SOL_CUSTOM, 0, &buf, 1);
        if (err) {
                log_err("Failed to call setsockopt");
                goto err;
        }
 
-       buf[0] = 0x00;
+       buf.u32 = 0x00;
        optlen = 4;
-       err = getsockopt(fd, SOL_CUSTOM, 0, buf, &optlen);
+       err = getsockopt(fd, SOL_CUSTOM, 0, &buf, &optlen);
        if (err) {
                log_err("Failed to call getsockopt");
                goto err;
@@ -84,37 +87,31 @@ static int getsetsockopt(void)
                log_err("Unexpected optlen %d != 1", optlen);
                goto err;
        }
-       if (buf[0] != 0x01) {
-               log_err("Unexpected buf[0] 0x%02x != 0x01", buf[0]);
+       if (buf.u8[0] != 0x01) {
+               log_err("Unexpected buf[0] 0x%02x != 0x01", buf.u8[0]);
                goto err;
        }
 
        /* SO_SNDBUF is overwritten */
 
-       buf[0] = 0x01;
-       buf[1] = 0x01;
-       buf[2] = 0x01;
-       buf[3] = 0x01;
-       err = setsockopt(fd, SOL_SOCKET, SO_SNDBUF, buf, 4);
+       buf.u32 = 0x01010101;
+       err = setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &buf, 4);
        if (err) {
                log_err("Failed to call setsockopt(SO_SNDBUF)");
                goto err;
        }
 
-       buf[0] = 0x00;
-       buf[1] = 0x00;
-       buf[2] = 0x00;
-       buf[3] = 0x00;
+       buf.u32 = 0x00;
        optlen = 4;
-       err = getsockopt(fd, SOL_SOCKET, SO_SNDBUF, buf, &optlen);
+       err = getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &buf, &optlen);
        if (err) {
                log_err("Failed to call getsockopt(SO_SNDBUF)");
                goto err;
        }
 
-       if (*(__u32 *)buf != 0x55AA*2) {
+       if (buf.u32 != 0x55AA*2) {
                log_err("Unexpected getsockopt(SO_SNDBUF) 0x%x != 0x55AA*2",
-                       *(__u32 *)buf);
+                       buf.u32);
                goto err;
        }