1 // SPDX-License-Identifier: GPL-2.0 2 #define _GNU_SOURCE 3 4 #include <inttypes.h> 5 #include <unistd.h> 6 #include <stdio.h> 7 8 #include <linux/unistd.h> 9 #include <linux/types.h> 10 #include <linux/mount.h> 11 #include <sys/syscall.h> 12 #include <sys/stat.h> 13 #include <sys/mman.h> 14 #include <sched.h> 15 #include <fcntl.h> 16 17 #include "../../kselftest.h" 18 #include "log.h" 19 20 static int sys_fsopen(const char *fsname, unsigned int flags) 21 { 22 return syscall(__NR_fsopen, fsname, flags); 23 } 24 25 static int sys_fsconfig(int fd, unsigned int cmd, const char *key, const char *value, int aux) 26 { 27 return syscall(__NR_fsconfig, fd, cmd, key, value, aux); 28 } 29 30 static int sys_fsmount(int fd, unsigned int flags, unsigned int attr_flags) 31 { 32 return syscall(__NR_fsmount, fd, flags, attr_flags); 33 } 34 static int sys_mount(const char *src, const char *tgt, const char *fst, 35 unsigned long flags, const void *data) 36 { 37 return syscall(__NR_mount, src, tgt, fst, flags, data); 38 } 39 static int sys_move_mount(int from_dfd, const char *from_pathname, 40 int to_dfd, const char *to_pathname, 41 unsigned int flags) 42 { 43 return syscall(__NR_move_mount, from_dfd, from_pathname, to_dfd, to_pathname, flags); 44 } 45 46 static long get_file_dev_and_inode(void *addr, struct statx *stx) 47 { 48 char buf[4096]; 49 FILE *mapf; 50 51 mapf = fopen("/proc/self/maps", "r"); 52 if (mapf == NULL) 53 return pr_perror("fopen(/proc/self/maps)"); 54 55 while (fgets(buf, sizeof(buf), mapf)) { 56 unsigned long start, end; 57 uint32_t maj, min; 58 __u64 ino; 59 60 if (sscanf(buf, "%lx-%lx %*s %*s %x:%x %llu", 61 &start, &end, &maj, &min, &ino) != 5) 62 return pr_perror("unable to parse: %s", buf); 63 if (start == (unsigned long)addr) { 64 stx->stx_dev_major = maj; 65 stx->stx_dev_minor = min; 66 stx->stx_ino = ino; 67 return 0; 68 } 69 } 70 71 return pr_err("unable to find the mapping"); 72 } 73 74 static int ovl_mount(void) 75 { 76 int tmpfs, fsfd, ovl; 77 78 fsfd = sys_fsopen("tmpfs", 0); 79 if (fsfd == -1) 80 return pr_perror("fsopen(tmpfs)"); 81 82 if (sys_fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0) == -1) 83 return pr_perror("FSCONFIG_CMD_CREATE"); 84 85 tmpfs = sys_fsmount(fsfd, 0, 0); 86 if (tmpfs == -1) 87 return pr_perror("fsmount"); 88 89 close(fsfd); 90 91 /* overlayfs can't be constructed on top of a detached mount. */ 92 if (sys_move_mount(tmpfs, "", AT_FDCWD, "/tmp", MOVE_MOUNT_F_EMPTY_PATH)) 93 return pr_perror("move_mount"); 94 close(tmpfs); 95 96 if (mkdir("/tmp/w", 0755) == -1 || 97 mkdir("/tmp/u", 0755) == -1 || 98 mkdir("/tmp/l", 0755) == -1) 99 return pr_perror("mkdir"); 100 101 fsfd = sys_fsopen("overlay", 0); 102 if (fsfd == -1) 103 return pr_perror("fsopen(overlay)"); 104 if (sys_fsconfig(fsfd, FSCONFIG_SET_STRING, "source", "test", 0) == -1 || 105 sys_fsconfig(fsfd, FSCONFIG_SET_STRING, "lowerdir", "/tmp/l", 0) == -1 || 106 sys_fsconfig(fsfd, FSCONFIG_SET_STRING, "upperdir", "/tmp/u", 0) == -1 || 107 sys_fsconfig(fsfd, FSCONFIG_SET_STRING, "workdir", "/tmp/w", 0) == -1) 108 return pr_perror("fsconfig"); 109 if (sys_fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0) == -1) 110 return pr_perror("fsconfig"); 111 ovl = sys_fsmount(fsfd, 0, 0); 112 if (ovl == -1) 113 return pr_perror("fsmount"); 114 115 return ovl; 116 } 117 118 /* 119 * Check that the file device and inode shown in /proc/pid/maps match values 120 * returned by stat(2). 121 */ 122 static int test(void) 123 { 124 struct statx stx, mstx; 125 int ovl, fd; 126 void *addr; 127 128 ovl = ovl_mount(); 129 if (ovl == -1) 130 return -1; 131 132 fd = openat(ovl, "test", O_RDWR | O_CREAT, 0644); 133 if (fd == -1) 134 return pr_perror("openat"); 135 136 addr = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED, fd, 0); 137 if (addr == MAP_FAILED) 138 return pr_perror("mmap"); 139 140 if (get_file_dev_and_inode(addr, &mstx)) 141 return -1; 142 if (statx(fd, "", AT_EMPTY_PATH | AT_STATX_SYNC_AS_STAT, STATX_INO, &stx)) 143 return pr_perror("statx"); 144 145 if (stx.stx_dev_major != mstx.stx_dev_major || 146 stx.stx_dev_minor != mstx.stx_dev_minor || 147 stx.stx_ino != mstx.stx_ino) 148 return pr_fail("unmatched dev:ino %x:%x:%llx (expected %x:%x:%llx)\n", 149 mstx.stx_dev_major, mstx.stx_dev_minor, mstx.stx_ino, 150 stx.stx_dev_major, stx.stx_dev_minor, stx.stx_ino); 151 152 ksft_test_result_pass("devices are matched\n"); 153 return 0; 154 } 155 156 int main(int argc, char **argv) 157 { 158 int fsfd; 159 160 fsfd = sys_fsopen("overlay", 0); 161 if (fsfd == -1) { 162 ksft_test_result_skip("unable to create overlay mount\n"); 163 return 1; 164 } 165 close(fsfd); 166 167 /* Create a new mount namespace to not care about cleaning test mounts. */ 168 if (unshare(CLONE_NEWNS) == -1) { 169 ksft_test_result_skip("unable to create a new mount namespace\n"); 170 return 1; 171 } 172 if (sys_mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) == -1) { 173 pr_perror("mount"); 174 return 1; 175 } 176 177 ksft_set_plan(1); 178 179 if (test()) 180 return 1; 181 182 ksft_exit_pass(); 183 return 0; 184 } 185