// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <linux/types.h>
#include <poll.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_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 __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;
bool ignore_child_result;
};
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)
{
int ret;
EXPECT_EQ(0, close(self->pidfd));
EXPECT_EQ(0, close(self->sk));
ret = wait_for_pid(self->pid);
if (!self->ignore_child_result)
EXPECT_EQ(0, ret);
}
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);
ret = sys_kcmp(getpid(), self->pid, KCMP_FILE, fd, self->remote_fd);
if (ret < 0 && errno == ENOSYS)
SKIP(return, "kcmp() syscall not supported");
EXPECT_EQ(ret, 0);
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);
}
TEST_F(child, no_strange_EBADF)
{
struct pollfd fds;
self->ignore_child_result = true;
fds.fd = self->pidfd;
fds.events = POLLIN;
ASSERT_EQ(kill(self->pid, SIGKILL), 0);
ASSERT_EQ(poll(&fds, 1, 5000), 1);
/*
* It used to be that pidfd_getfd() could race with the exiting thread
* between exit_files() and release_task(), and get a non-null task
* with a NULL files struct, and you'd get EBADF, which was slightly
* confusing.
*/
errno = 0;
EXPECT_EQ(sys_pidfd_getfd(self->pidfd, self->remote_fd, 0), -1);
EXPECT_EQ(errno, ESRCH);
}
#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
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