bpf: use prefix_len in test_tag when reading fdinfo

We currently used len instead of prefix_len for the strncmp() in
fdinfo on the prog_tag. It still worked as we matched on the correct
output line also with first 8 instead of 10 chars, but lets fix it
properly to use the intended length.

Fixes: 62b64660262a ("bpf: add prog tag test case to bpf selftests")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/tools/testing/selftests/bpf/test_tag.c b/tools/testing/selftests/bpf/test_tag.c
index 6ab4793b3d16976260662f03268def3c7bb3a55f..5f7c602f47d17b5c39f5ce97c6e6a1ddc2534f64 100644 (file)
--- a/tools/testing/selftests/bpf/test_tag.c
+++ b/tools/testing/selftests/bpf/test_tag.c
@@ -99,7 +99,7 @@ static void tag_from_fdinfo(int fd_prog, uint8_t *tag, uint32_t len)
        assert(fp);
 
        while (fgets(buff, sizeof(buff), fp)) {
-               if (strncmp(buff, "prog_tag:\t", len))
+               if (strncmp(buff, "prog_tag:\t", prefix_len))
                        continue;
                ret = hex2bin(tag, buff + prefix_len, len);
                break;