Add some basic tests for nested listeners.
Cc: linux-kernel@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Cc: bpf@vger.kernel.org Cc: Kees Cook kees@kernel.org Cc: Andy Lutomirski luto@amacapital.net Cc: Will Drewry wad@chromium.org Cc: Jonathan Corbet corbet@lwn.net Cc: Shuah Khan shuah@kernel.org Cc: Aleksa Sarai cyphar@cyphar.com Cc: Tycho Andersen tycho@tycho.pizza Cc: Andrei Vagin avagin@gmail.com Cc: Christian Brauner brauner@kernel.org Cc: Stéphane Graber stgraber@stgraber.org Signed-off-by: Alexander Mikhalitsyn aleksandr.mikhalitsyn@canonical.com --- tools/testing/selftests/seccomp/seccomp_bpf.c | 162 ++++++++++++++++++ 1 file changed, 162 insertions(+)
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index fc4910d35342..0bf02d04fe15 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -293,6 +293,10 @@ struct seccomp_notif_addfd_big { #define SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV (1UL << 5) #endif
+#ifndef SECCOMP_FILTER_FLAG_ALLOW_NESTED_LISTENERS +#define SECCOMP_FILTER_FLAG_ALLOW_NESTED_LISTENERS (1UL << 6) +#endif + #ifndef seccomp int seccomp(unsigned int op, unsigned int flags, void *args) { @@ -4408,6 +4412,164 @@ TEST(user_notification_sync) ASSERT_EQ(status, 0); }
+/* from kernel/seccomp.c */ +#define MAX_LISTENERS_PER_PATH 8 + +TEST(user_notification_nested_limits) +{ + pid_t pid; + long ret; + int i, status, listeners[MAX_LISTENERS_PER_PATH]; + + 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, + }; + + 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!"); + } + + /* Install 6 levels of listeners and allow nesting. */ + for (i = 0; i < 6; i++) { + listeners[i] = user_notif_syscall(__NR_getppid, + SECCOMP_FILTER_FLAG_NEW_LISTENER | + SECCOMP_FILTER_FLAG_ALLOW_NESTED_LISTENERS); + ASSERT_GE(listeners[i], 0); + + /* Add some no-op filters for grins. */ + EXPECT_EQ(seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog), 0); + } + + /* Check behavior when nesting is not allowed. */ + pid = fork(); + ASSERT_GE(pid, 0); + if (pid == 0) { + /* Install a next listener in the chain without nesting allowed. */ + listeners[6] = user_notif_syscall(__NR_getppid, + SECCOMP_FILTER_FLAG_NEW_LISTENER); + if (listeners[6] < 0) + exit(1); + + /* Add some no-op filters for grins. */ + ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog); + if (ret != 0) + exit(2); + + ret = user_notif_syscall(__NR_getppid, + SECCOMP_FILTER_FLAG_NEW_LISTENER); + /* Installing a next listener in the chain should result in EBUSY. */ + exit((ret >= 0 || errno != EBUSY) ? 3 : 0); + } + + EXPECT_EQ(waitpid(pid, &status, 0), pid); + EXPECT_EQ(true, WIFEXITED(status)); + EXPECT_EQ(0, WEXITSTATUS(status)); + + /* Install more filters with listeners to reach nesting levels limit. */ + for (; i < MAX_LISTENERS_PER_PATH; i++) { + listeners[i] = user_notif_syscall(__NR_getppid, + SECCOMP_FILTER_FLAG_NEW_LISTENER | + SECCOMP_FILTER_FLAG_ALLOW_NESTED_LISTENERS); + ASSERT_GE(listeners[i], 0); + + /* Add some no-op filters for grins. */ + EXPECT_EQ(seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog), 0); + } + + /* Installing a next listener in the chain should result in ELOOP. */ + EXPECT_EQ(user_notif_syscall(__NR_getppid, + SECCOMP_FILTER_FLAG_NEW_LISTENER), + -1); + EXPECT_EQ(errno, ELOOP); +} + +TEST(user_notification_nested) +{ + pid_t pid; + long ret; + int i, status, listeners[6]; + struct seccomp_notif req = {}; + struct seccomp_notif_resp resp = {}; + + 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, + }; + + 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!"); + } + + /* Install 6 levels of listeners and allow nesting. */ + for (i = 0; i < 6; i++) { + listeners[i] = user_notif_syscall(__NR_getppid, + SECCOMP_FILTER_FLAG_NEW_LISTENER | + SECCOMP_FILTER_FLAG_ALLOW_NESTED_LISTENERS); + ASSERT_GE(listeners[i], 0); + + /* Add some no-op filters for grins. */ + EXPECT_EQ(seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog), 0); + } + + pid = fork(); + ASSERT_GE(pid, 0); + + if (pid == 0) { + ret = syscall(__NR_getppid); + exit(ret != (USER_NOTIF_MAGIC-3)); + } + + /* + * We want to have the following picture: + * + * | Listener level (i) | Listener decision | + * |--------------------|-------------------| + * | 0 | WHATEVER | + * | 1 | WHATEVER | + * | 2 | WHATEVER | + * | 3 | RETURN | <-- stop here + * | 4 | CONTINUE SYSCALL | + * | 5 | CONTINUE SYSCALL | <- start here (current->seccomp.filter) + * + * First listener who receives a notification is level 5, then 4, + * then we expect to stop on level 3 and return from syscall with + * (USER_NOTIF_MAGIC - 3) return value. + */ + for (i = 6 - 1; i >= 3; i--) { + memset(&req, 0, sizeof(req)); + EXPECT_EQ(ioctl(listeners[i], SECCOMP_IOCTL_NOTIF_RECV, &req), 0); + EXPECT_EQ(req.pid, pid); + EXPECT_EQ(req.data.nr, __NR_getppid); + + memset(&resp, 0, sizeof(resp)); + resp.id = req.id; + + if (i == 5 || i == 4) { + resp.flags = SECCOMP_USER_NOTIF_FLAG_CONTINUE; + } else { + resp.error = 0; + resp.val = USER_NOTIF_MAGIC - i; + } + + EXPECT_EQ(ioctl(listeners[i], SECCOMP_IOCTL_NOTIF_SEND, &resp), 0); + } + + EXPECT_EQ(waitpid(pid, &status, 0), pid); + EXPECT_EQ(true, WIFEXITED(status)); + EXPECT_EQ(0, WEXITSTATUS(status)); + + for (i = 0; i < 6; i++) + close(listeners[i]); +}
/* Make sure PTRACE_O_SUSPEND_SECCOMP requires CAP_SYS_ADMIN. */ FIXTURE(O_SUSPEND_SECCOMP) {