@@ -2,3 +2,4 @@ pidfd_open_test
pidfd_poll_test
pidfd_test
pidfd_wait
+pidfd_getfd_test
@@ -1,7 +1,7 @@
# SPDX-License-Identifier: GPL-2.0-only
CFLAGS += -g -I../../../../usr/include/ -pthread
-TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test pidfd_poll_test pidfd_wait
+TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test pidfd_poll_test pidfd_wait pidfd_getfd_test
include ../lib.mk
@@ -36,6 +36,10 @@
#define __NR_clone3 -1
#endif
+#ifndef __NR_pidfd_getfd
+#define __NR_pidfd_getfd -1
+#endif
+
/*
* The kernel reserves 300 pids via RESERVED_PIDS in kernel/pid.c
* That means, when it wraps around any pid < 300 will be skipped.
@@ -84,4 +88,9 @@ static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
}
+static inline int sys_pidfd_getfd(int pidfd, int fd, int flags)
+{
+ return syscall(__NR_pidfd_getfd, pidfd, fd, flags);
+}
+
#endif /* __PIDFD_H */
new file mode 100644
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <linux/types.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <linux/kcmp.h>
+
+#include "pidfd.h"
+#include "../kselftest.h"
+#include "../kselftest_harness.h"
+
+/*
+ * UNKNOWN_FD is an fd number that should never exist in the child, as it is
+ * used to check the negative case.
+ */
+#define UNKNOWN_FD 111
+#define UID_NOBODY 65535
+
+static int sys_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1,
+ unsigned long idx2)
+{
+ return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2);
+}
+
+static int sys_memfd_create(const char *name, unsigned int flags)
+{
+ return syscall(__NR_memfd_create, name, flags);
+}
+
+static int __child(int sk, int memfd)
+{
+ int ret;
+ char buf;
+
+ /*
+ * Ensure we don't leave around a bunch of orphaned children if our
+ * tests fail.
+ */
+ ret = prctl(PR_SET_PDEATHSIG, SIGKILL);
+ if (ret) {
+ fprintf(stderr, "%s: Child could not set DEATHSIG\n",
+ strerror(errno));
+ return -1;
+ }
+
+ ret = send(sk, &memfd, sizeof(memfd), 0);
+ if (ret != sizeof(memfd)) {
+ fprintf(stderr, "%s: Child failed to send fd number\n",
+ strerror(errno));
+ return -1;
+ }
+
+ /*
+ * The fixture setup is completed at this point. The tests will run.
+ *
+ * This blocking recv enables the parent to message the child.
+ * Either we will read 'P' off of the sk, indicating that we need
+ * to disable ptrace, or we will read a 0, indicating that the other
+ * side has closed the sk. This occurs during fixture teardown time,
+ * indicating that the child should exit.
+ */
+ while ((ret = recv(sk, &buf, sizeof(buf), 0)) > 0) {
+ if (buf == 'P') {
+ ret = prctl(PR_SET_DUMPABLE, 0);
+ if (ret < 0) {
+ fprintf(stderr,
+ "%s: Child failed to disable ptrace\n",
+ strerror(errno));
+ return -1;
+ }
+ } else {
+ fprintf(stderr, "Child received unknown command %c\n",
+ buf);
+ return -1;
+ }
+ ret = send(sk, &buf, sizeof(buf), 0);
+ if (ret != 1) {
+ fprintf(stderr, "%s: Child failed to ack\n",
+ strerror(errno));
+ return -1;
+ }
+ }
+ if (ret < 0) {
+ fprintf(stderr, "%s: Child failed to read from socket\n",
+ strerror(errno));
+ return -1;
+ }
+
+ return 0;
+}
+
+static int child(int sk)
+{
+ int memfd, ret;
+
+ memfd = sys_memfd_create("test", 0);
+ if (memfd < 0) {
+ fprintf(stderr, "%s: Child could not create memfd\n",
+ strerror(errno));
+ ret = -1;
+ } else {
+ ret = __child(sk, memfd);
+ close(memfd);
+ }
+
+ close(sk);
+ return ret;
+}
+
+FIXTURE(child)
+{
+ /*
+ * remote_fd is the number of the FD which we are trying to retrieve
+ * from the child.
+ */
+ int remote_fd;
+ /* pid points to the child which we are fetching FDs from */
+ pid_t pid;
+ /* pidfd is the pidfd of the child */
+ int pidfd;
+ /*
+ * sk is our side of the socketpair used to communicate with the child.
+ * When it is closed, the child will exit.
+ */
+ int sk;
+};
+
+FIXTURE_SETUP(child)
+{
+ int ret, sk_pair[2];
+
+ ASSERT_EQ(0, socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair)) {
+ TH_LOG("%s: failed to create socketpair", strerror(errno));
+ }
+ self->sk = sk_pair[0];
+
+ self->pid = fork();
+ ASSERT_GE(self->pid, 0);
+
+ if (self->pid == 0) {
+ close(sk_pair[0]);
+ if (child(sk_pair[1]))
+ _exit(EXIT_FAILURE);
+ _exit(EXIT_SUCCESS);
+ }
+
+ close(sk_pair[1]);
+
+ self->pidfd = sys_pidfd_open(self->pid, 0);
+ ASSERT_GE(self->pidfd, 0);
+
+ /*
+ * Wait for the child to complete setup. It'll send the remote memfd's
+ * number when ready.
+ */
+ ret = recv(sk_pair[0], &self->remote_fd, sizeof(self->remote_fd), 0);
+ ASSERT_EQ(sizeof(self->remote_fd), ret);
+}
+
+FIXTURE_TEARDOWN(child)
+{
+ EXPECT_EQ(0, close(self->pidfd));
+ EXPECT_EQ(0, close(self->sk));
+
+ EXPECT_EQ(0, wait_for_pid(self->pid));
+}
+
+TEST_F(child, disable_ptrace)
+{
+ int uid, fd;
+ char c;
+
+ /*
+ * Turn into nobody if we're root, to avoid CAP_SYS_PTRACE
+ *
+ * The tests should run in their own process, so even this test fails,
+ * it shouldn't result in subsequent tests failing.
+ */
+ uid = getuid();
+ if (uid == 0)
+ ASSERT_EQ(0, seteuid(UID_NOBODY));
+
+ ASSERT_EQ(1, send(self->sk, "P", 1, 0));
+ ASSERT_EQ(1, recv(self->sk, &c, 1, 0));
+
+ fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);
+ EXPECT_EQ(-1, fd);
+ EXPECT_EQ(EPERM, errno);
+
+ if (uid == 0)
+ ASSERT_EQ(0, seteuid(0));
+}
+
+TEST_F(child, fetch_fd)
+{
+ int fd, ret;
+
+ fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);
+ ASSERT_GE(fd, 0);
+
+ EXPECT_EQ(0, sys_kcmp(getpid(), self->pid, KCMP_FILE, fd, self->remote_fd));
+
+ ret = fcntl(fd, F_GETFD);
+ ASSERT_GE(ret, 0);
+ EXPECT_GE(ret & FD_CLOEXEC, 0);
+
+ close(fd);
+}
+
+TEST_F(child, test_unknown_fd)
+{
+ int fd;
+
+ fd = sys_pidfd_getfd(self->pidfd, UNKNOWN_FD, 0);
+ EXPECT_EQ(-1, fd) {
+ TH_LOG("getfd succeeded while fetching unknown fd");
+ };
+ EXPECT_EQ(EBADF, errno) {
+ TH_LOG("%s: getfd did not get EBADF", strerror(errno));
+ }
+}
+
+TEST(flags_set)
+{
+ ASSERT_EQ(-1, sys_pidfd_getfd(0, 0, 1));
+ EXPECT_EQ(errno, EINVAL);
+}
+
+#if __NR_pidfd_getfd == -1
+int main(void)
+{
+ fprintf(stderr, "__NR_pidfd_getfd undefined. The pidfd_getfd syscall is unavailable. Test aborting\n");
+ return KSFT_SKIP;
+}
+#else
+TEST_HARNESS_MAIN
+#endif
The following tests: * Fetch FD, and then compare via kcmp * Make sure getfd can be blocked by blocking ptrace_may_access * Making sure fetching bad FDs fails * Make sure trying to set flags to non-zero results in an EINVAL Signed-off-by: Sargun Dhillon <sargun@sargun.me> --- tools/testing/selftests/pidfd/.gitignore | 1 + tools/testing/selftests/pidfd/Makefile | 2 +- tools/testing/selftests/pidfd/pidfd.h | 9 + .../selftests/pidfd/pidfd_getfd_test.c | 249 ++++++++++++++++++ 4 files changed, 260 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/pidfd/pidfd_getfd_test.c