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
sys_fsopen(const char * fsname,unsigned int flags)21 static int sys_fsopen(const char *fsname, unsigned int flags)
22 {
23 return syscall(__NR_fsopen, fsname, flags);
24 }
25
sys_fsconfig(int fd,unsigned int cmd,const char * key,const char * value,int aux)26 static 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
sys_fsmount(int fd,unsigned int flags,unsigned int attr_flags)31 static int sys_fsmount(int fd, unsigned int flags, unsigned int attr_flags)
32 {
33 return syscall(__NR_fsmount, fd, flags, attr_flags);
34 }
35
sys_move_mount(int from_dfd,const char * from_pathname,int to_dfd,const char * to_pathname,unsigned int flags)36 static 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
get_file_dev_and_inode(void * addr,struct statx * stx)43 static 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
ovl_mount(void)71 static 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 */
test(void)119 static 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
main(int argc,char ** argv)153 int 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 }
183