From 0eebfed2954f152259cae0ad57b91d3ea92968e8 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Fri, 20 Sep 2019 10:30:07 +0200 Subject: [PATCH] seccomp: test SECCOMP_USER_NOTIF_FLAG_CONTINUE 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 Cc: Andy Lutomirski Cc: Will Drewry Cc: Shuah Khan Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Martin KaFai Lau Cc: Song Liu Cc: Yonghong Song Cc: Tycho Andersen CC: Tyler Hicks Cc: stable@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Cc: netdev@vger.kernel.org Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20190920083007.11475-4-christian.brauner@ubuntu.com Signed-off-by: Kees Cook --- tools/testing/selftests/seccomp/seccomp_bpf.c | 107 ++++++++++++++++++ 1 file changed, 107 insertions(+) diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index b505bb062d07..47d65d9b77f6 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -44,6 +44,7 @@ #include #include #include +#include #include #include @@ -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) @@ -3486,6 +3491,108 @@ 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; +#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(1); + + dup_fd = dup(pipe_fds[0]); + if (dup_fd < 0) + exit(1); + + self = getpid(); + + ret = filecmp(self, self, pipe_fds[0], dup_fd); + if (ret) + exit(2); + + exit(0); + } + + 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)) { + if (WEXITSTATUS(status) == 2) { + XFAIL(return, "Kernel does not support kcmp() syscall"); + return; + } + } +} + /* * TODO: * - add microbenchmarks