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