1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * security/tomoyo/mount.c
4  *
5  * Copyright (C) 2005-2011  NTT DATA CORPORATION
6  */
7 
8 #include <linux/slab.h>
9 #include <uapi/linux/mount.h>
10 #include "common.h"
11 
12 /* String table for special mount operations. */
13 static const char * const tomoyo_mounts[TOMOYO_MAX_SPECIAL_MOUNT] = {
14 	[TOMOYO_MOUNT_BIND]            = "--bind",
15 	[TOMOYO_MOUNT_MOVE]            = "--move",
16 	[TOMOYO_MOUNT_REMOUNT]         = "--remount",
17 	[TOMOYO_MOUNT_MAKE_UNBINDABLE] = "--make-unbindable",
18 	[TOMOYO_MOUNT_MAKE_PRIVATE]    = "--make-private",
19 	[TOMOYO_MOUNT_MAKE_SLAVE]      = "--make-slave",
20 	[TOMOYO_MOUNT_MAKE_SHARED]     = "--make-shared",
21 };
22 
23 /**
24  * tomoyo_audit_mount_log - Audit mount log.
25  *
26  * @r: Pointer to "struct tomoyo_request_info".
27  *
28  * Returns 0 on success, negative value otherwise.
29  */
tomoyo_audit_mount_log(struct tomoyo_request_info * r)30 static int tomoyo_audit_mount_log(struct tomoyo_request_info *r)
31 {
32 	return tomoyo_supervisor(r, "file mount %s %s %s 0x%lX\n",
33 				 r->param.mount.dev->name,
34 				 r->param.mount.dir->name,
35 				 r->param.mount.type->name,
36 				 r->param.mount.flags);
37 }
38 
39 /**
40  * tomoyo_check_mount_acl - Check permission for path path path number operation.
41  *
42  * @r:   Pointer to "struct tomoyo_request_info".
43  * @ptr: Pointer to "struct tomoyo_acl_info".
44  *
45  * Returns true if granted, false otherwise.
46  */
tomoyo_check_mount_acl(struct tomoyo_request_info * r,const struct tomoyo_acl_info * ptr)47 static bool tomoyo_check_mount_acl(struct tomoyo_request_info *r,
48 				   const struct tomoyo_acl_info *ptr)
49 {
50 	const struct tomoyo_mount_acl *acl =
51 		container_of(ptr, typeof(*acl), head);
52 
53 	return tomoyo_compare_number_union(r->param.mount.flags,
54 					   &acl->flags) &&
55 		tomoyo_compare_name_union(r->param.mount.type,
56 					  &acl->fs_type) &&
57 		tomoyo_compare_name_union(r->param.mount.dir,
58 					  &acl->dir_name) &&
59 		(!r->param.mount.need_dev ||
60 		 tomoyo_compare_name_union(r->param.mount.dev,
61 					   &acl->dev_name));
62 }
63 
64 /**
65  * tomoyo_mount_acl - Check permission for mount() operation.
66  *
67  * @r:        Pointer to "struct tomoyo_request_info".
68  * @dev_name: Name of device file. Maybe NULL.
69  * @dir:      Pointer to "struct path".
70  * @type:     Name of filesystem type.
71  * @flags:    Mount options.
72  *
73  * Returns 0 on success, negative value otherwise.
74  *
75  * Caller holds tomoyo_read_lock().
76  */
tomoyo_mount_acl(struct tomoyo_request_info * r,const char * dev_name,const struct path * dir,const char * type,unsigned long flags)77 static int tomoyo_mount_acl(struct tomoyo_request_info *r,
78 			    const char *dev_name,
79 			    const struct path *dir, const char *type,
80 			    unsigned long flags)
81 {
82 	struct tomoyo_obj_info obj = { };
83 	struct path path;
84 	struct file_system_type *fstype = NULL;
85 	const char *requested_type = NULL;
86 	const char *requested_dir_name = NULL;
87 	const char *requested_dev_name = NULL;
88 	struct tomoyo_path_info rtype;
89 	struct tomoyo_path_info rdev;
90 	struct tomoyo_path_info rdir;
91 	int need_dev = 0;
92 	int error = -ENOMEM;
93 
94 	r->obj = &obj;
95 
96 	/* Get fstype. */
97 	requested_type = tomoyo_encode(type);
98 	if (!requested_type)
99 		goto out;
100 	rtype.name = requested_type;
101 	tomoyo_fill_path_info(&rtype);
102 
103 	/* Get mount point. */
104 	obj.path2 = *dir;
105 	requested_dir_name = tomoyo_realpath_from_path(dir);
106 	if (!requested_dir_name) {
107 		error = -ENOMEM;
108 		goto out;
109 	}
110 	rdir.name = requested_dir_name;
111 	tomoyo_fill_path_info(&rdir);
112 
113 	/* Compare fs name. */
114 	if (type == tomoyo_mounts[TOMOYO_MOUNT_REMOUNT]) {
115 		/* dev_name is ignored. */
116 	} else if (type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE] ||
117 		   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE] ||
118 		   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE] ||
119 		   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED]) {
120 		/* dev_name is ignored. */
121 	} else if (type == tomoyo_mounts[TOMOYO_MOUNT_BIND] ||
122 		   type == tomoyo_mounts[TOMOYO_MOUNT_MOVE]) {
123 		need_dev = -1; /* dev_name is a directory */
124 	} else {
125 		fstype = get_fs_type(type);
126 		if (!fstype) {
127 			error = -ENODEV;
128 			goto out;
129 		}
130 		if (fstype->fs_flags & FS_REQUIRES_DEV)
131 			/* dev_name is a block device file. */
132 			need_dev = 1;
133 	}
134 	if (need_dev) {
135 		/* Get mount point or device file. */
136 		if (!dev_name || kern_path(dev_name, LOOKUP_FOLLOW, &path)) {
137 			error = -ENOENT;
138 			goto out;
139 		}
140 		obj.path1 = path;
141 		requested_dev_name = tomoyo_realpath_from_path(&path);
142 		if (!requested_dev_name) {
143 			error = -ENOENT;
144 			goto out;
145 		}
146 	} else {
147 		/* Map dev_name to "<NULL>" if no dev_name given. */
148 		if (!dev_name)
149 			dev_name = "<NULL>";
150 		requested_dev_name = tomoyo_encode(dev_name);
151 		if (!requested_dev_name) {
152 			error = -ENOMEM;
153 			goto out;
154 		}
155 	}
156 	rdev.name = requested_dev_name;
157 	tomoyo_fill_path_info(&rdev);
158 	r->param_type = TOMOYO_TYPE_MOUNT_ACL;
159 	r->param.mount.need_dev = need_dev;
160 	r->param.mount.dev = &rdev;
161 	r->param.mount.dir = &rdir;
162 	r->param.mount.type = &rtype;
163 	r->param.mount.flags = flags;
164 	do {
165 		tomoyo_check_acl(r, tomoyo_check_mount_acl);
166 		error = tomoyo_audit_mount_log(r);
167 	} while (error == TOMOYO_RETRY_REQUEST);
168  out:
169 	kfree(requested_dev_name);
170 	kfree(requested_dir_name);
171 	if (fstype)
172 		put_filesystem(fstype);
173 	kfree(requested_type);
174 	/* Drop refcount obtained by kern_path(). */
175 	if (obj.path1.dentry)
176 		path_put(&obj.path1);
177 	return error;
178 }
179 
180 /**
181  * tomoyo_mount_permission - Check permission for mount() operation.
182  *
183  * @dev_name:  Name of device file. Maybe NULL.
184  * @path:      Pointer to "struct path".
185  * @type:      Name of filesystem type. Maybe NULL.
186  * @flags:     Mount options.
187  * @data_page: Optional data. Maybe NULL.
188  *
189  * Returns 0 on success, negative value otherwise.
190  */
tomoyo_mount_permission(const char * dev_name,const struct path * path,const char * type,unsigned long flags,void * data_page)191 int tomoyo_mount_permission(const char *dev_name, const struct path *path,
192 			    const char *type, unsigned long flags,
193 			    void *data_page)
194 {
195 	struct tomoyo_request_info r;
196 	int error;
197 	int idx;
198 
199 	if (tomoyo_init_request_info(&r, NULL, TOMOYO_MAC_FILE_MOUNT)
200 	    == TOMOYO_CONFIG_DISABLED)
201 		return 0;
202 	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
203 		flags &= ~MS_MGC_MSK;
204 	if (flags & MS_REMOUNT) {
205 		type = tomoyo_mounts[TOMOYO_MOUNT_REMOUNT];
206 		flags &= ~MS_REMOUNT;
207 	} else if (flags & MS_BIND) {
208 		type = tomoyo_mounts[TOMOYO_MOUNT_BIND];
209 		flags &= ~MS_BIND;
210 	} else if (flags & MS_SHARED) {
211 		if (flags & (MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
212 			return -EINVAL;
213 		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED];
214 		flags &= ~MS_SHARED;
215 	} else if (flags & MS_PRIVATE) {
216 		if (flags & (MS_SHARED | MS_SLAVE | MS_UNBINDABLE))
217 			return -EINVAL;
218 		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE];
219 		flags &= ~MS_PRIVATE;
220 	} else if (flags & MS_SLAVE) {
221 		if (flags & (MS_SHARED | MS_PRIVATE | MS_UNBINDABLE))
222 			return -EINVAL;
223 		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE];
224 		flags &= ~MS_SLAVE;
225 	} else if (flags & MS_UNBINDABLE) {
226 		if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE))
227 			return -EINVAL;
228 		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE];
229 		flags &= ~MS_UNBINDABLE;
230 	} else if (flags & MS_MOVE) {
231 		type = tomoyo_mounts[TOMOYO_MOUNT_MOVE];
232 		flags &= ~MS_MOVE;
233 	}
234 	if (!type)
235 		type = "<NULL>";
236 	idx = tomoyo_read_lock();
237 	error = tomoyo_mount_acl(&r, dev_name, path, type, flags);
238 	tomoyo_read_unlock(idx);
239 	return error;
240 }
241