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
 20static int sys_fsopen(const char *fsname, unsigned int flags)
 21{
 22	return syscall(__NR_fsopen, fsname, flags);
 23}
 24
 25static 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
 30static int sys_fsmount(int fd, unsigned int flags, unsigned int attr_flags)
 31{
 32	return syscall(__NR_fsmount, fd, flags, attr_flags);
 33}
 34static 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}
 39static 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
 46static 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
 74static 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 */
122static 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
156int 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}