mnt_idmapping.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_MNT_IDMAPPING_H
  3#define _LINUX_MNT_IDMAPPING_H
  4
  5#include <linux/types.h>
  6#include <linux/uidgid.h>
  7
  8struct mnt_idmap;
  9struct user_namespace;
 10
 11extern struct mnt_idmap nop_mnt_idmap;
 12extern struct mnt_idmap invalid_mnt_idmap;
 13extern struct user_namespace init_user_ns;
 14
 15typedef struct {
 16	uid_t val;
 17} vfsuid_t;
 18
 19typedef struct {
 20	gid_t val;
 21} vfsgid_t;
 22
 23static_assert(sizeof(vfsuid_t) == sizeof(kuid_t));
 24static_assert(sizeof(vfsgid_t) == sizeof(kgid_t));
 25static_assert(offsetof(vfsuid_t, val) == offsetof(kuid_t, val));
 26static_assert(offsetof(vfsgid_t, val) == offsetof(kgid_t, val));
 27
 28static inline bool is_valid_mnt_idmap(const struct mnt_idmap *idmap)
 29{
 30	return idmap != &nop_mnt_idmap && idmap != &invalid_mnt_idmap;
 31}
 32
 33#ifdef CONFIG_MULTIUSER
 34static inline uid_t __vfsuid_val(vfsuid_t uid)
 35{
 36	return uid.val;
 37}
 38
 39static inline gid_t __vfsgid_val(vfsgid_t gid)
 40{
 41	return gid.val;
 42}
 43#else
 44static inline uid_t __vfsuid_val(vfsuid_t uid)
 45{
 46	return 0;
 47}
 48
 49static inline gid_t __vfsgid_val(vfsgid_t gid)
 50{
 51	return 0;
 52}
 53#endif
 54
 55static inline bool vfsuid_valid(vfsuid_t uid)
 56{
 57	return __vfsuid_val(uid) != (uid_t)-1;
 58}
 59
 60static inline bool vfsgid_valid(vfsgid_t gid)
 61{
 62	return __vfsgid_val(gid) != (gid_t)-1;
 63}
 64
 65static inline bool vfsuid_eq(vfsuid_t left, vfsuid_t right)
 66{
 67	return vfsuid_valid(left) && __vfsuid_val(left) == __vfsuid_val(right);
 68}
 69
 70static inline bool vfsgid_eq(vfsgid_t left, vfsgid_t right)
 71{
 72	return vfsgid_valid(left) && __vfsgid_val(left) == __vfsgid_val(right);
 73}
 74
 75/**
 76 * vfsuid_eq_kuid - check whether kuid and vfsuid have the same value
 77 * @vfsuid: the vfsuid to compare
 78 * @kuid: the kuid to compare
 79 *
 80 * Check whether @vfsuid and @kuid have the same values.
 81 *
 82 * Return: true if @vfsuid and @kuid have the same value, false if not.
 83 * Comparison between two invalid uids returns false.
 84 */
 85static inline bool vfsuid_eq_kuid(vfsuid_t vfsuid, kuid_t kuid)
 86{
 87	return vfsuid_valid(vfsuid) && __vfsuid_val(vfsuid) == __kuid_val(kuid);
 88}
 89
 90/**
 91 * vfsgid_eq_kgid - check whether kgid and vfsgid have the same value
 92 * @vfsgid: the vfsgid to compare
 93 * @kgid: the kgid to compare
 94 *
 95 * Check whether @vfsgid and @kgid have the same values.
 96 *
 97 * Return: true if @vfsgid and @kgid have the same value, false if not.
 98 * Comparison between two invalid gids returns false.
 99 */
100static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t kgid)
101{
102	return vfsgid_valid(vfsgid) && __vfsgid_val(vfsgid) == __kgid_val(kgid);
103}
104
105/*
106 * vfs{g,u}ids are created from k{g,u}ids.
107 * We don't allow them to be created from regular {u,g}id.
108 */
109#define VFSUIDT_INIT(val) (vfsuid_t){ __kuid_val(val) }
110#define VFSGIDT_INIT(val) (vfsgid_t){ __kgid_val(val) }
111
112#define INVALID_VFSUID VFSUIDT_INIT(INVALID_UID)
113#define INVALID_VFSGID VFSGIDT_INIT(INVALID_GID)
114
115/*
116 * Allow a vfs{g,u}id to be used as a k{g,u}id where we want to compare
117 * whether the mapped value is identical to value of a k{g,u}id.
118 */
119#define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) }
120#define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) }
121
122int vfsgid_in_group_p(vfsgid_t vfsgid);
123
124struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap);
125void mnt_idmap_put(struct mnt_idmap *idmap);
126
127vfsuid_t make_vfsuid(struct mnt_idmap *idmap,
128		     struct user_namespace *fs_userns, kuid_t kuid);
129
130vfsgid_t make_vfsgid(struct mnt_idmap *idmap,
131		     struct user_namespace *fs_userns, kgid_t kgid);
132
133kuid_t from_vfsuid(struct mnt_idmap *idmap,
134		   struct user_namespace *fs_userns, vfsuid_t vfsuid);
135
136kgid_t from_vfsgid(struct mnt_idmap *idmap,
137		   struct user_namespace *fs_userns, vfsgid_t vfsgid);
138
139/**
140 * vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
141 * @idmap: the mount's idmapping
142 * @fs_userns: the filesystem's idmapping
143 * @vfsuid: vfsuid to be mapped
144 *
145 * Check whether @vfsuid has a mapping in the filesystem idmapping. Use this
146 * function to check whether the filesystem idmapping has a mapping for
147 * @vfsuid.
148 *
149 * Return: true if @vfsuid has a mapping in the filesystem, false if not.
150 */
151static inline bool vfsuid_has_fsmapping(struct mnt_idmap *idmap,
152					struct user_namespace *fs_userns,
153					vfsuid_t vfsuid)
154{
155	return uid_valid(from_vfsuid(idmap, fs_userns, vfsuid));
156}
157
158static inline bool vfsuid_has_mapping(struct user_namespace *userns,
159				      vfsuid_t vfsuid)
160{
161	return from_kuid(userns, AS_KUIDT(vfsuid)) != (uid_t)-1;
162}
163
164/**
165 * vfsuid_into_kuid - convert vfsuid into kuid
166 * @vfsuid: the vfsuid to convert
167 *
168 * This can be used when a vfsuid is committed as a kuid.
169 *
170 * Return: a kuid with the value of @vfsuid
171 */
172static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
173{
174	return AS_KUIDT(vfsuid);
175}
176
177/**
178 * vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
179 * @idmap: the mount's idmapping
180 * @fs_userns: the filesystem's idmapping
181 * @vfsgid: vfsgid to be mapped
182 *
183 * Check whether @vfsgid has a mapping in the filesystem idmapping. Use this
184 * function to check whether the filesystem idmapping has a mapping for
185 * @vfsgid.
186 *
187 * Return: true if @vfsgid has a mapping in the filesystem, false if not.
188 */
189static inline bool vfsgid_has_fsmapping(struct mnt_idmap *idmap,
190					struct user_namespace *fs_userns,
191					vfsgid_t vfsgid)
192{
193	return gid_valid(from_vfsgid(idmap, fs_userns, vfsgid));
194}
195
196static inline bool vfsgid_has_mapping(struct user_namespace *userns,
197				      vfsgid_t vfsgid)
198{
199	return from_kgid(userns, AS_KGIDT(vfsgid)) != (gid_t)-1;
200}
201
202/**
203 * vfsgid_into_kgid - convert vfsgid into kgid
204 * @vfsgid: the vfsgid to convert
205 *
206 * This can be used when a vfsgid is committed as a kgid.
207 *
208 * Return: a kgid with the value of @vfsgid
209 */
210static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
211{
212	return AS_KGIDT(vfsgid);
213}
214
215/**
216 * mapped_fsuid - return caller's fsuid mapped according to an idmapping
217 * @idmap: the mount's idmapping
218 * @fs_userns: the filesystem's idmapping
219 *
220 * Use this helper to initialize a new vfs or filesystem object based on
221 * the caller's fsuid. A common example is initializing the i_uid field of
222 * a newly allocated inode triggered by a creation event such as mkdir or
223 * O_CREAT. Other examples include the allocation of quotas for a specific
224 * user.
225 *
226 * Return: the caller's current fsuid mapped up according to @idmap.
227 */
228static inline kuid_t mapped_fsuid(struct mnt_idmap *idmap,
229				  struct user_namespace *fs_userns)
230{
231	return from_vfsuid(idmap, fs_userns, VFSUIDT_INIT(current_fsuid()));
232}
233
234/**
235 * mapped_fsgid - return caller's fsgid mapped according to an idmapping
236 * @idmap: the mount's idmapping
237 * @fs_userns: the filesystem's idmapping
238 *
239 * Use this helper to initialize a new vfs or filesystem object based on
240 * the caller's fsgid. A common example is initializing the i_gid field of
241 * a newly allocated inode triggered by a creation event such as mkdir or
242 * O_CREAT. Other examples include the allocation of quotas for a specific
243 * user.
244 *
245 * Return: the caller's current fsgid mapped up according to @idmap.
246 */
247static inline kgid_t mapped_fsgid(struct mnt_idmap *idmap,
248				  struct user_namespace *fs_userns)
249{
250	return from_vfsgid(idmap, fs_userns, VFSGIDT_INIT(current_fsgid()));
251}
252
253#endif /* _LINUX_MNT_IDMAPPING_H */