On 9/19/19 3:59 AM, Christian Brauner wrote:

Test whether a syscall can be performed after having been intercepted by the seccomp notifier. The test uses dup() and kcmp() since it allows us to nicely test whether the dup() syscall actually succeeded by comparing whether the fds refer to the same underlying struct file.

Signed-off-by: Christian Brauner christian.brauner@ubuntu.com Cc: Kees Cook keescook@chromium.org Cc: Andy Lutomirski luto@amacapital.net Cc: Will Drewry wad@chromium.org Cc: Shuah Khan shuah@kernel.org Cc: Alexei Starovoitov ast@kernel.org Cc: Daniel Borkmann daniel@iogearbox.net Cc: Martin KaFai Lau kafai@fb.com Cc: Song Liu songliubraving@fb.com Cc: Yonghong Song yhs@fb.com Cc: Tycho Andersen tycho@tycho.ws CC: Tyler Hicks tyhicks@canonical.com Cc: stable@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Cc: netdev@vger.kernel.org Cc: bpf@vger.kernel.org

---

/* v1 */

• Christian Brauner christian.brauner@ubuntu.com:
  • adapt to new flag name SECCOMP_USER_NOTIF_FLAG_CONTINUE

/* v0 */ Link: https://lore.kernel.org/r/20190918084833.9369-5-christian.brauner@ubuntu.com

---

tools/testing/selftests/seccomp/seccomp_bpf.c | 102 ++++++++++++++++++ 1 file changed, 102 insertions(+)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index e996d7b7fd6e..b0966599acb5 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -44,6 +44,7 @@ #include <sys/times.h> #include <sys/socket.h> #include <sys/ioctl.h> +#include <linux/kcmp.h> #include <unistd.h> #include <sys/syscall.h> @@ -167,6 +168,10 @@ struct seccomp_metadata { #define SECCOMP_RET_USER_NOTIF 0x7fc00000U +#ifndef SECCOMP_USER_NOTIF_FLAG_CONTINUE +#define SECCOMP_USER_NOTIF_FLAG_CONTINUE 0x00000001 +#endif

• #define SECCOMP_IOC_MAGIC '!' #define SECCOMP_IO(nr) _IO(SECCOMP_IOC_MAGIC, nr) #define SECCOMP_IOR(nr, type) _IOR(SECCOMP_IOC_MAGIC, nr, type)

@@ -3481,6 +3486,103 @@ TEST(seccomp_get_notif_sizes) EXPECT_EQ(sizes.seccomp_notif_resp, sizeof(struct seccomp_notif_resp)); } +static int filecmp(pid_t pid1, pid_t pid2, int fd1, int fd2) +{ +#ifdef __NR_kcmp

• return syscall(__NR_kcmp, pid1, pid2, KCMP_FILE, fd1, fd2);

+#else

• errno = ENOSYS;
• return -1;

This should be SKIP for kselftest so this isn't counted a failure. In this case test can't be run because of a missing dependency.

+#endif +}

+TEST(user_notification_continue) +{

• pid_t pid;
• long ret;
• int status, listener;
• struct seccomp_notif req = {};
• struct seccomp_notif_resp resp = {};
• struct pollfd pollfd;
• ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
• ASSERT_EQ(0, ret) {

• TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
  

• }
• listener = user_trap_syscall(__NR_dup, SECCOMP_FILTER_FLAG_NEW_LISTENER);
• ASSERT_GE(listener, 0);
• pid = fork();
• ASSERT_GE(pid, 0);
• if (pid == 0) {

• int dup_fd, pipe_fds[2];
  

• pid_t self;
  

• ret = pipe(pipe_fds);
  

• if (ret < 0)
  

• 	exit(EXIT_FAILURE);
  

• dup_fd = dup(pipe_fds[0]);
  

• if (dup_fd < 0)
  

• 	exit(EXIT_FAILURE);
  

• self = getpid();
  

• ret = filecmp(self, self, pipe_fds[0], dup_fd);
  

• if (ret)
  

• 	exit(EXIT_FAILURE);
  

• exit(EXIT_SUCCESS);
  

• }
• pollfd.fd = listener;
• pollfd.events = POLLIN | POLLOUT;
• EXPECT_GT(poll(&pollfd, 1, -1), 0);
• EXPECT_EQ(pollfd.revents, POLLIN);
• EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
• pollfd.fd = listener;
• pollfd.events = POLLIN | POLLOUT;
• EXPECT_GT(poll(&pollfd, 1, -1), 0);
• EXPECT_EQ(pollfd.revents, POLLOUT);
• EXPECT_EQ(req.data.nr, __NR_dup);
• resp.id = req.id;
• resp.flags = SECCOMP_USER_NOTIF_FLAG_CONTINUE;
• /*

• * Verify that setting SECCOMP_USER_NOTIF_FLAG_CONTINUE enforces other
  

• * args be set to 0.
  

• */
  

• resp.error = 0;
• resp.val = USER_NOTIF_MAGIC;
• EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), -1);
• EXPECT_EQ(errno, EINVAL);
• resp.error = USER_NOTIF_MAGIC;
• resp.val = 0;
• EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), -1);
• EXPECT_EQ(errno, EINVAL);
• resp.error = 0;
• resp.val = 0;
• EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0) {

• if (errno == EINVAL)
  

• 	XFAIL(goto skip, "Kernel does not support SECCOMP_USER_NOTIF_FLAG_CONTINUE");
  

• }

+skip:

• EXPECT_EQ(waitpid(pid, &status, 0), pid);
• EXPECT_EQ(true, WIFEXITED(status));
• EXPECT_EQ(0, WEXITSTATUS(status));

+}

• /*
  • TODO:
  • • add microbenchmarks

thanks, -- Shuah