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1// SPDX-License-Identifier: GPL-2.02 3#define _GNU_SOURCE4#include <errno.h>5#include <fcntl.h>6#include <limits.h>7#include <linux/types.h>8#include <poll.h>9#include <sched.h>10#include <signal.h>11#include <stdio.h>12#include <stdlib.h>13#include <string.h>14#include <syscall.h>15#include <sys/prctl.h>16#include <sys/wait.h>17#include <unistd.h>18#include <sys/socket.h>19#include <linux/kcmp.h>20 21#include "pidfd.h"22#include "../kselftest_harness.h"23 24/*25 * UNKNOWN_FD is an fd number that should never exist in the child, as it is26 * used to check the negative case.27 */28#define UNKNOWN_FD 11129#define UID_NOBODY 6553530 31static int sys_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1,32 unsigned long idx2)33{34 return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2);35}36 37static int __child(int sk, int memfd)38{39 int ret;40 char buf;41 42 /*43 * Ensure we don't leave around a bunch of orphaned children if our44 * tests fail.45 */46 ret = prctl(PR_SET_PDEATHSIG, SIGKILL);47 if (ret) {48 fprintf(stderr, "%s: Child could not set DEATHSIG\n",49 strerror(errno));50 return -1;51 }52 53 ret = send(sk, &memfd, sizeof(memfd), 0);54 if (ret != sizeof(memfd)) {55 fprintf(stderr, "%s: Child failed to send fd number\n",56 strerror(errno));57 return -1;58 }59 60 /*61 * The fixture setup is completed at this point. The tests will run.62 *63 * This blocking recv enables the parent to message the child.64 * Either we will read 'P' off of the sk, indicating that we need65 * to disable ptrace, or we will read a 0, indicating that the other66 * side has closed the sk. This occurs during fixture teardown time,67 * indicating that the child should exit.68 */69 while ((ret = recv(sk, &buf, sizeof(buf), 0)) > 0) {70 if (buf == 'P') {71 ret = prctl(PR_SET_DUMPABLE, 0);72 if (ret < 0) {73 fprintf(stderr,74 "%s: Child failed to disable ptrace\n",75 strerror(errno));76 return -1;77 }78 } else {79 fprintf(stderr, "Child received unknown command %c\n",80 buf);81 return -1;82 }83 ret = send(sk, &buf, sizeof(buf), 0);84 if (ret != 1) {85 fprintf(stderr, "%s: Child failed to ack\n",86 strerror(errno));87 return -1;88 }89 }90 if (ret < 0) {91 fprintf(stderr, "%s: Child failed to read from socket\n",92 strerror(errno));93 return -1;94 }95 96 return 0;97}98 99static int child(int sk)100{101 int memfd, ret;102 103 memfd = sys_memfd_create("test", 0);104 if (memfd < 0) {105 fprintf(stderr, "%s: Child could not create memfd\n",106 strerror(errno));107 ret = -1;108 } else {109 ret = __child(sk, memfd);110 close(memfd);111 }112 113 close(sk);114 return ret;115}116 117FIXTURE(child)118{119 /*120 * remote_fd is the number of the FD which we are trying to retrieve121 * from the child.122 */123 int remote_fd;124 /* pid points to the child which we are fetching FDs from */125 pid_t pid;126 /* pidfd is the pidfd of the child */127 int pidfd;128 /*129 * sk is our side of the socketpair used to communicate with the child.130 * When it is closed, the child will exit.131 */132 int sk;133 bool ignore_child_result;134};135 136FIXTURE_SETUP(child)137{138 int ret, sk_pair[2];139 140 ASSERT_EQ(0, socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair)) {141 TH_LOG("%s: failed to create socketpair", strerror(errno));142 }143 self->sk = sk_pair[0];144 145 self->pid = fork();146 ASSERT_GE(self->pid, 0);147 148 if (self->pid == 0) {149 close(sk_pair[0]);150 if (child(sk_pair[1]))151 _exit(EXIT_FAILURE);152 _exit(EXIT_SUCCESS);153 }154 155 close(sk_pair[1]);156 157 self->pidfd = sys_pidfd_open(self->pid, 0);158 ASSERT_GE(self->pidfd, 0);159 160 /*161 * Wait for the child to complete setup. It'll send the remote memfd's162 * number when ready.163 */164 ret = recv(sk_pair[0], &self->remote_fd, sizeof(self->remote_fd), 0);165 ASSERT_EQ(sizeof(self->remote_fd), ret);166}167 168FIXTURE_TEARDOWN(child)169{170 int ret;171 172 EXPECT_EQ(0, close(self->pidfd));173 EXPECT_EQ(0, close(self->sk));174 175 ret = wait_for_pid(self->pid);176 if (!self->ignore_child_result)177 EXPECT_EQ(0, ret);178}179 180TEST_F(child, disable_ptrace)181{182 int uid, fd;183 char c;184 185 /*186 * Turn into nobody if we're root, to avoid CAP_SYS_PTRACE187 *188 * The tests should run in their own process, so even this test fails,189 * it shouldn't result in subsequent tests failing.190 */191 uid = getuid();192 if (uid == 0)193 ASSERT_EQ(0, seteuid(UID_NOBODY));194 195 ASSERT_EQ(1, send(self->sk, "P", 1, 0));196 ASSERT_EQ(1, recv(self->sk, &c, 1, 0));197 198 fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);199 EXPECT_EQ(-1, fd);200 EXPECT_EQ(EPERM, errno);201 202 if (uid == 0)203 ASSERT_EQ(0, seteuid(0));204}205 206TEST_F(child, fetch_fd)207{208 int fd, ret;209 210 fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);211 ASSERT_GE(fd, 0);212 213 ret = sys_kcmp(getpid(), self->pid, KCMP_FILE, fd, self->remote_fd);214 if (ret < 0 && errno == ENOSYS)215 SKIP(return, "kcmp() syscall not supported");216 EXPECT_EQ(ret, 0);217 218 ret = fcntl(fd, F_GETFD);219 ASSERT_GE(ret, 0);220 EXPECT_GE(ret & FD_CLOEXEC, 0);221 222 close(fd);223}224 225TEST_F(child, test_unknown_fd)226{227 int fd;228 229 fd = sys_pidfd_getfd(self->pidfd, UNKNOWN_FD, 0);230 EXPECT_EQ(-1, fd) {231 TH_LOG("getfd succeeded while fetching unknown fd");232 };233 EXPECT_EQ(EBADF, errno) {234 TH_LOG("%s: getfd did not get EBADF", strerror(errno));235 }236}237 238TEST(flags_set)239{240 ASSERT_EQ(-1, sys_pidfd_getfd(0, 0, 1));241 EXPECT_EQ(errno, EINVAL);242}243 244TEST_F(child, no_strange_EBADF)245{246 struct pollfd fds;247 248 self->ignore_child_result = true;249 250 fds.fd = self->pidfd;251 fds.events = POLLIN;252 253 ASSERT_EQ(kill(self->pid, SIGKILL), 0);254 ASSERT_EQ(poll(&fds, 1, 5000), 1);255 256 /*257 * It used to be that pidfd_getfd() could race with the exiting thread258 * between exit_files() and release_task(), and get a non-null task259 * with a NULL files struct, and you'd get EBADF, which was slightly260 * confusing.261 */262 errno = 0;263 EXPECT_EQ(sys_pidfd_getfd(self->pidfd, self->remote_fd, 0), -1);264 EXPECT_EQ(errno, ESRCH);265}266 267#if __NR_pidfd_getfd == -1268int main(void)269{270 fprintf(stderr, "__NR_pidfd_getfd undefined. The pidfd_getfd syscall is unavailable. Test aborting\n");271 return KSFT_SKIP;272}273#else274TEST_HARNESS_MAIN275#endif276