Re: [PATCH bpf-next v4 7/8] selftests/bpf: Fix fd cleanup in sk_lookup test

Similar to the fix in commit:
e31eec77e4ab ("bpf: selftests: Fix fd cleanup in get_branch_snapshot")

We use designated initializer to set fds to -1 without breaking on
future changes to MAX_SERVER constant denoting the array size.

The particular close(0) occurs on non-reuseport tests, so it can be seen
with -n 115/{2,3} but not 115/4. This can cause problems with future
tests if they depend on BTF fd never being acquired as fd 0, breaking
internal libbpf assumptions.

Fixes: 0ab5539f8584 ("selftests/bpf: Tests for BPF_SK_LOOKUP attach point")
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Song Liu <redacted>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/testing/selftests/bpf/prog_tests/sk_lookup.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/sk_lookup.c b/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
index aee41547e7f4..cbee46d2d525 100644
--- a/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
+++ b/tools/testing/selftests/bpf/prog_tests/sk_lookup.c

@@ -598,7 +598,7 @@ static void query_lookup_prog(struct test_sk_lookup *skel)

 static void run_lookup_prog(const struct test *t)
 {
-       int server_fds[MAX_SERVERS] = { -1 };
+       int server_fds[] = { [0 ... MAX_SERVERS - 1] = -1 };

        int client_fd, reuse_conn_fd = -1;
        struct bpf_link *lookup_link;
        int i, err;

@@ -663,8 +663,9 @@ static void run_lookup_prog(const struct test *t)
        if (reuse_conn_fd != -1)
                close(reuse_conn_fd);
        for (i = 0; i < ARRAY_SIZE(server_fds); i++) {
-               if (server_fds[i] != -1)
-                       close(server_fds[i]);
+               if (server_fds[i] == -1)
+                       break;
+               close(server_fds[i]);
        }
        bpf_link__destroy(lookup_link);
 }

@@ -1053,7 +1054,7 @@ static void run_sk_assign(struct test_sk_lookup *skel,
                          struct bpf_program *lookup_prog,
                          const char *remote_ip, const char *local_ip)
 {
-       int server_fds[MAX_SERVERS] = { -1 };
+       int server_fds[] = { [0 ... MAX_SERVERS - 1] = -1 };
        struct bpf_sk_lookup ctx;
        __u64 server_cookie;
        int i, err;

@@ -1097,8 +1098,9 @@ static void run_sk_assign(struct test_sk_lookup *skel,

 close_servers:
        for (i = 0; i < ARRAY_SIZE(server_fds); i++) {
-               if (server_fds[i] != -1)
-                       close(server_fds[i]);
+               if (server_fds[i] == -1)
+                       break;
+               close(server_fds[i]);
        }
 }

--

2.33.1