selftests/bpf: Test freeing sockmap/sockhash with a socket in it

Commit 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear
down") introduced sleeping issues inside RCU critical sections and while
holding a spinlock on sockmap/sockhash tear-down. There has to be at least
one socket in the map for the problem to surface.

This adds a test that triggers the warnings for broken locking rules. Not a
fix per se, but rather tooling to verify the accompanying fixes. Run on a
VM with 1 vCPU to reproduce the warnings.

Fixes: 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear down")
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200206111652.694507-4-jakub@cloudflare.com

diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
new file mode 100644 (file)
index 0000000..07f5b46
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Cloudflare
+
+#include "test_progs.h"
+
+static int connected_socket_v4(void)
+{
+       struct sockaddr_in addr = {
+               .sin_family = AF_INET,
+               .sin_port = htons(80),
+               .sin_addr = { inet_addr("127.0.0.1") },
+       };
+       socklen_t len = sizeof(addr);
+       int s, repair, err;
+
+       s = socket(AF_INET, SOCK_STREAM, 0);
+       if (CHECK_FAIL(s == -1))
+               goto error;
+
+       repair = TCP_REPAIR_ON;
+       err = setsockopt(s, SOL_TCP, TCP_REPAIR, &repair, sizeof(repair));
+       if (CHECK_FAIL(err))
+               goto error;
+
+       err = connect(s, (struct sockaddr *)&addr, len);
+       if (CHECK_FAIL(err))
+               goto error;
+
+       repair = TCP_REPAIR_OFF_NO_WP;
+       err = setsockopt(s, SOL_TCP, TCP_REPAIR, &repair, sizeof(repair));
+       if (CHECK_FAIL(err))
+               goto error;
+
+       return s;
+error:
+       perror(__func__);
+       close(s);
+       return -1;
+}
+
+/* Create a map, populate it with one socket, and free the map. */
+static void test_sockmap_create_update_free(enum bpf_map_type map_type)
+{
+       const int zero = 0;
+       int s, map, err;
+
+       s = connected_socket_v4();
+       if (CHECK_FAIL(s == -1))
+               return;
+
+       map = bpf_create_map(map_type, sizeof(int), sizeof(int), 1, 0);
+       if (CHECK_FAIL(map == -1)) {
+               perror("bpf_create_map");
+               goto out;
+       }
+
+       err = bpf_map_update_elem(map, &zero, &s, BPF_NOEXIST);
+       if (CHECK_FAIL(err)) {
+               perror("bpf_map_update");
+               goto out;
+       }
+
+out:
+       close(map);
+       close(s);
+}
+
+void test_sockmap_basic(void)
+{
+       if (test__start_subtest("sockmap create_update_free"))
+               test_sockmap_create_update_free(BPF_MAP_TYPE_SOCKMAP);
+       if (test__start_subtest("sockhash create_update_free"))
+               test_sockmap_create_update_free(BPF_MAP_TYPE_SOCKHASH);
+}