seccomp: add a selftest for get_metadata

Let's test that we get the flags correctly, and that we preserve the filter
index across the ptrace(PTRACE_SECCOMP_GET_METADATA) correctly.

Signed-off-by: Tycho Andersen <tycho@tycho.ws>
CC: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 24dbf63..92db488 100644 (file)
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -141,6 +141,15 @@ struct seccomp_data {
 #define SECCOMP_FILTER_FLAG_LOG 2
 #endif
 
+#ifndef PTRACE_SECCOMP_GET_METADATA
+#define PTRACE_SECCOMP_GET_METADATA    0x420d
+
+struct seccomp_metadata {
+       __u64 filter_off;       /* Input: which filter */
+       __u64 flags;             /* Output: filter's flags */
+};
+#endif
+
 #ifndef seccomp
 int seccomp(unsigned int op, unsigned int flags, void *args)
 {
@@ -2845,6 +2854,58 @@ TEST(get_action_avail)
        EXPECT_EQ(errno, EOPNOTSUPP);
 }
 
+TEST(get_metadata)
+{
+       pid_t pid;
+       int pipefd[2];
+       char buf;
+       struct seccomp_metadata md;
+
+       ASSERT_EQ(0, pipe(pipefd));
+
+       pid = fork();
+       ASSERT_GE(pid, 0);
+       if (pid == 0) {
+               struct sock_filter filter[] = {
+                       BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+               };
+               struct sock_fprog prog = {
+                       .len = (unsigned short)ARRAY_SIZE(filter),
+                       .filter = filter,
+               };
+
+               /* one with log, one without */
+               ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER,
+                                    SECCOMP_FILTER_FLAG_LOG, &prog));
+               ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog));
+
+               ASSERT_EQ(0, close(pipefd[0]));
+               ASSERT_EQ(1, write(pipefd[1], "1", 1));
+               ASSERT_EQ(0, close(pipefd[1]));
+
+               while (1)
+                       sleep(100);
+       }
+
+       ASSERT_EQ(0, close(pipefd[1]));
+       ASSERT_EQ(1, read(pipefd[0], &buf, 1));
+
+       ASSERT_EQ(0, ptrace(PTRACE_ATTACH, pid));
+       ASSERT_EQ(pid, waitpid(pid, NULL, 0));
+
+       md.filter_off = 0;
+       ASSERT_EQ(sizeof(md), ptrace(PTRACE_SECCOMP_GET_METADATA, pid, sizeof(md), &md));
+       EXPECT_EQ(md.flags, SECCOMP_FILTER_FLAG_LOG);
+       EXPECT_EQ(md.filter_off, 0);
+
+       md.filter_off = 1;
+       ASSERT_EQ(sizeof(md), ptrace(PTRACE_SECCOMP_GET_METADATA, pid, sizeof(md), &md));
+       EXPECT_EQ(md.flags, 0);
+       EXPECT_EQ(md.filter_off, 1);
+
+       ASSERT_EQ(0, kill(pid, SIGKILL));
+}
+
 /*
  * TODO:
  * - add microbenchmarks