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 
8 struct user_namespace;
9 /*
10  * Carries the initial idmapping of 0:0:4294967295 which is an identity
11  * mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
12  * mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
13  */
14 extern struct user_namespace init_user_ns;
15 
16 typedef struct {
17 	uid_t val;
18 } vfsuid_t;
19 
20 typedef struct {
21 	gid_t val;
22 } vfsgid_t;
23 
24 static_assert(sizeof(vfsuid_t) == sizeof(kuid_t));
25 static_assert(sizeof(vfsgid_t) == sizeof(kgid_t));
26 static_assert(offsetof(vfsuid_t, val) == offsetof(kuid_t, val));
27 static_assert(offsetof(vfsgid_t, val) == offsetof(kgid_t, val));
28 
29 #ifdef CONFIG_MULTIUSER
__vfsuid_val(vfsuid_t uid)30 static inline uid_t __vfsuid_val(vfsuid_t uid)
31 {
32 	return uid.val;
33 }
34 
__vfsgid_val(vfsgid_t gid)35 static inline gid_t __vfsgid_val(vfsgid_t gid)
36 {
37 	return gid.val;
38 }
39 #else
__vfsuid_val(vfsuid_t uid)40 static inline uid_t __vfsuid_val(vfsuid_t uid)
41 {
42 	return 0;
43 }
44 
__vfsgid_val(vfsgid_t gid)45 static inline gid_t __vfsgid_val(vfsgid_t gid)
46 {
47 	return 0;
48 }
49 #endif
50 
vfsuid_valid(vfsuid_t uid)51 static inline bool vfsuid_valid(vfsuid_t uid)
52 {
53 	return __vfsuid_val(uid) != (uid_t)-1;
54 }
55 
vfsgid_valid(vfsgid_t gid)56 static inline bool vfsgid_valid(vfsgid_t gid)
57 {
58 	return __vfsgid_val(gid) != (gid_t)-1;
59 }
60 
vfsuid_eq(vfsuid_t left,vfsuid_t right)61 static inline bool vfsuid_eq(vfsuid_t left, vfsuid_t right)
62 {
63 	return vfsuid_valid(left) && __vfsuid_val(left) == __vfsuid_val(right);
64 }
65 
vfsgid_eq(vfsgid_t left,vfsgid_t right)66 static inline bool vfsgid_eq(vfsgid_t left, vfsgid_t right)
67 {
68 	return vfsgid_valid(left) && __vfsgid_val(left) == __vfsgid_val(right);
69 }
70 
71 /**
72  * vfsuid_eq_kuid - check whether kuid and vfsuid have the same value
73  * @vfsuid: the vfsuid to compare
74  * @kuid: the kuid to compare
75  *
76  * Check whether @vfsuid and @kuid have the same values.
77  *
78  * Return: true if @vfsuid and @kuid have the same value, false if not.
79  * Comparison between two invalid uids returns false.
80  */
vfsuid_eq_kuid(vfsuid_t vfsuid,kuid_t kuid)81 static inline bool vfsuid_eq_kuid(vfsuid_t vfsuid, kuid_t kuid)
82 {
83 	return vfsuid_valid(vfsuid) && __vfsuid_val(vfsuid) == __kuid_val(kuid);
84 }
85 
86 /**
87  * vfsgid_eq_kgid - check whether kgid and vfsgid have the same value
88  * @vfsgid: the vfsgid to compare
89  * @kgid: the kgid to compare
90  *
91  * Check whether @vfsgid and @kgid have the same values.
92  *
93  * Return: true if @vfsgid and @kgid have the same value, false if not.
94  * Comparison between two invalid gids returns false.
95  */
vfsgid_eq_kgid(vfsgid_t vfsgid,kgid_t kgid)96 static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t kgid)
97 {
98 	return vfsgid_valid(vfsgid) && __vfsgid_val(vfsgid) == __kgid_val(kgid);
99 }
100 
101 /*
102  * vfs{g,u}ids are created from k{g,u}ids.
103  * We don't allow them to be created from regular {u,g}id.
104  */
105 #define VFSUIDT_INIT(val) (vfsuid_t){ __kuid_val(val) }
106 #define VFSGIDT_INIT(val) (vfsgid_t){ __kgid_val(val) }
107 
108 #define INVALID_VFSUID VFSUIDT_INIT(INVALID_UID)
109 #define INVALID_VFSGID VFSGIDT_INIT(INVALID_GID)
110 
111 /*
112  * Allow a vfs{g,u}id to be used as a k{g,u}id where we want to compare
113  * whether the mapped value is identical to value of a k{g,u}id.
114  */
115 #define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) }
116 #define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) }
117 
118 #ifdef CONFIG_MULTIUSER
119 /**
120  * vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups
121  * @vfsgid: the mnt gid to match
122  *
123  * This function can be used to determine whether @vfsuid matches any of the
124  * caller's groups.
125  *
126  * Return: 1 if vfsuid matches caller's groups, 0 if not.
127  */
vfsgid_in_group_p(vfsgid_t vfsgid)128 static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
129 {
130 	return in_group_p(AS_KGIDT(vfsgid));
131 }
132 #else
vfsgid_in_group_p(vfsgid_t vfsgid)133 static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
134 {
135 	return 1;
136 }
137 #endif
138 
139 /**
140  * initial_idmapping - check whether this is the initial mapping
141  * @ns: idmapping to check
142  *
143  * Check whether this is the initial mapping, mapping 0 to 0, 1 to 1,
144  * [...], 1000 to 1000 [...].
145  *
146  * Return: true if this is the initial mapping, false if not.
147  */
initial_idmapping(const struct user_namespace * ns)148 static inline bool initial_idmapping(const struct user_namespace *ns)
149 {
150 	return ns == &init_user_ns;
151 }
152 
153 /**
154  * no_idmapping - check whether we can skip remapping a kuid/gid
155  * @mnt_userns: the mount's idmapping
156  * @fs_userns: the filesystem's idmapping
157  *
158  * This function can be used to check whether a remapping between two
159  * idmappings is required.
160  * An idmapped mount is a mount that has an idmapping attached to it that
161  * is different from the filsystem's idmapping and the initial idmapping.
162  * If the initial mapping is used or the idmapping of the mount and the
163  * filesystem are identical no remapping is required.
164  *
165  * Return: true if remapping can be skipped, false if not.
166  */
no_idmapping(const struct user_namespace * mnt_userns,const struct user_namespace * fs_userns)167 static inline bool no_idmapping(const struct user_namespace *mnt_userns,
168 				const struct user_namespace *fs_userns)
169 {
170 	return initial_idmapping(mnt_userns) || mnt_userns == fs_userns;
171 }
172 
173 /**
174  * make_vfsuid - map a filesystem kuid into a mnt_userns
175  * @mnt_userns: the mount's idmapping
176  * @fs_userns: the filesystem's idmapping
177  * @kuid : kuid to be mapped
178  *
179  * Take a @kuid and remap it from @fs_userns into @mnt_userns. Use this
180  * function when preparing a @kuid to be reported to userspace.
181  *
182  * If no_idmapping() determines that this is not an idmapped mount we can
183  * simply return @kuid unchanged.
184  * If initial_idmapping() tells us that the filesystem is not mounted with an
185  * idmapping we know the value of @kuid won't change when calling
186  * from_kuid() so we can simply retrieve the value via __kuid_val()
187  * directly.
188  *
189  * Return: @kuid mapped according to @mnt_userns.
190  * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
191  * returned.
192  */
193 
make_vfsuid(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,kuid_t kuid)194 static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
195 				   struct user_namespace *fs_userns,
196 				   kuid_t kuid)
197 {
198 	uid_t uid;
199 
200 	if (no_idmapping(mnt_userns, fs_userns))
201 		return VFSUIDT_INIT(kuid);
202 	if (initial_idmapping(fs_userns))
203 		uid = __kuid_val(kuid);
204 	else
205 		uid = from_kuid(fs_userns, kuid);
206 	if (uid == (uid_t)-1)
207 		return INVALID_VFSUID;
208 	return VFSUIDT_INIT(make_kuid(mnt_userns, uid));
209 }
210 
mapped_kuid_fs(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,kuid_t kuid)211 static inline kuid_t mapped_kuid_fs(struct user_namespace *mnt_userns,
212 				    struct user_namespace *fs_userns,
213 				    kuid_t kuid)
214 {
215 	return AS_KUIDT(make_vfsuid(mnt_userns, fs_userns, kuid));
216 }
217 
218 /**
219  * make_vfsgid - map a filesystem kgid into a mnt_userns
220  * @mnt_userns: the mount's idmapping
221  * @fs_userns: the filesystem's idmapping
222  * @kgid : kgid to be mapped
223  *
224  * Take a @kgid and remap it from @fs_userns into @mnt_userns. Use this
225  * function when preparing a @kgid to be reported to userspace.
226  *
227  * If no_idmapping() determines that this is not an idmapped mount we can
228  * simply return @kgid unchanged.
229  * If initial_idmapping() tells us that the filesystem is not mounted with an
230  * idmapping we know the value of @kgid won't change when calling
231  * from_kgid() so we can simply retrieve the value via __kgid_val()
232  * directly.
233  *
234  * Return: @kgid mapped according to @mnt_userns.
235  * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
236  * returned.
237  */
238 
make_vfsgid(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,kgid_t kgid)239 static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
240 				   struct user_namespace *fs_userns,
241 				   kgid_t kgid)
242 {
243 	gid_t gid;
244 
245 	if (no_idmapping(mnt_userns, fs_userns))
246 		return VFSGIDT_INIT(kgid);
247 	if (initial_idmapping(fs_userns))
248 		gid = __kgid_val(kgid);
249 	else
250 		gid = from_kgid(fs_userns, kgid);
251 	if (gid == (gid_t)-1)
252 		return INVALID_VFSGID;
253 	return VFSGIDT_INIT(make_kgid(mnt_userns, gid));
254 }
255 
mapped_kgid_fs(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,kgid_t kgid)256 static inline kgid_t mapped_kgid_fs(struct user_namespace *mnt_userns,
257 				    struct user_namespace *fs_userns,
258 				    kgid_t kgid)
259 {
260 	return AS_KGIDT(make_vfsgid(mnt_userns, fs_userns, kgid));
261 }
262 
263 /**
264  * from_vfsuid - map a vfsuid into the filesystem idmapping
265  * @mnt_userns: the mount's idmapping
266  * @fs_userns: the filesystem's idmapping
267  * @vfsuid : vfsuid to be mapped
268  *
269  * Map @vfsuid into the filesystem idmapping. This function has to be used in
270  * order to e.g. write @vfsuid to inode->i_uid.
271  *
272  * Return: @vfsuid mapped into the filesystem idmapping
273  */
from_vfsuid(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,vfsuid_t vfsuid)274 static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
275 				 struct user_namespace *fs_userns,
276 				 vfsuid_t vfsuid)
277 {
278 	uid_t uid;
279 
280 	if (no_idmapping(mnt_userns, fs_userns))
281 		return AS_KUIDT(vfsuid);
282 	uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
283 	if (uid == (uid_t)-1)
284 		return INVALID_UID;
285 	if (initial_idmapping(fs_userns))
286 		return KUIDT_INIT(uid);
287 	return make_kuid(fs_userns, uid);
288 }
289 
290 /**
291  * mapped_kuid_user - map a user kuid into a mnt_userns
292  * @mnt_userns: the mount's idmapping
293  * @fs_userns: the filesystem's idmapping
294  * @kuid : kuid to be mapped
295  *
296  * Use the idmapping of @mnt_userns to remap a @kuid into @fs_userns. Use this
297  * function when preparing a @kuid to be written to disk or inode.
298  *
299  * If no_idmapping() determines that this is not an idmapped mount we can
300  * simply return @kuid unchanged.
301  * If initial_idmapping() tells us that the filesystem is not mounted with an
302  * idmapping we know the value of @kuid won't change when calling
303  * make_kuid() so we can simply retrieve the value via KUIDT_INIT()
304  * directly.
305  *
306  * Return: @kuid mapped according to @mnt_userns.
307  * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
308  * returned.
309  */
mapped_kuid_user(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,kuid_t kuid)310 static inline kuid_t mapped_kuid_user(struct user_namespace *mnt_userns,
311 				      struct user_namespace *fs_userns,
312 				      kuid_t kuid)
313 {
314 	return from_vfsuid(mnt_userns, fs_userns, VFSUIDT_INIT(kuid));
315 }
316 
317 /**
318  * vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
319  * @mnt_userns: the mount's idmapping
320  * @fs_userns: the filesystem's idmapping
321  * @vfsuid: vfsuid to be mapped
322  *
323  * Check whether @vfsuid has a mapping in the filesystem idmapping. Use this
324  * function to check whether the filesystem idmapping has a mapping for
325  * @vfsuid.
326  *
327  * Return: true if @vfsuid has a mapping in the filesystem, false if not.
328  */
vfsuid_has_fsmapping(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,vfsuid_t vfsuid)329 static inline bool vfsuid_has_fsmapping(struct user_namespace *mnt_userns,
330 					struct user_namespace *fs_userns,
331 					vfsuid_t vfsuid)
332 {
333 	return uid_valid(from_vfsuid(mnt_userns, fs_userns, vfsuid));
334 }
335 
336 /**
337  * vfsuid_into_kuid - convert vfsuid into kuid
338  * @vfsuid: the vfsuid to convert
339  *
340  * This can be used when a vfsuid is committed as a kuid.
341  *
342  * Return: a kuid with the value of @vfsuid
343  */
vfsuid_into_kuid(vfsuid_t vfsuid)344 static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
345 {
346 	return AS_KUIDT(vfsuid);
347 }
348 
349 /**
350  * from_vfsgid - map a vfsgid into the filesystem idmapping
351  * @mnt_userns: the mount's idmapping
352  * @fs_userns: the filesystem's idmapping
353  * @vfsgid : vfsgid to be mapped
354  *
355  * Map @vfsgid into the filesystem idmapping. This function has to be used in
356  * order to e.g. write @vfsgid to inode->i_gid.
357  *
358  * Return: @vfsgid mapped into the filesystem idmapping
359  */
from_vfsgid(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,vfsgid_t vfsgid)360 static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
361 				 struct user_namespace *fs_userns,
362 				 vfsgid_t vfsgid)
363 {
364 	gid_t gid;
365 
366 	if (no_idmapping(mnt_userns, fs_userns))
367 		return AS_KGIDT(vfsgid);
368 	gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
369 	if (gid == (gid_t)-1)
370 		return INVALID_GID;
371 	if (initial_idmapping(fs_userns))
372 		return KGIDT_INIT(gid);
373 	return make_kgid(fs_userns, gid);
374 }
375 
376 /**
377  * mapped_kgid_user - map a user kgid into a mnt_userns
378  * @mnt_userns: the mount's idmapping
379  * @fs_userns: the filesystem's idmapping
380  * @kgid : kgid to be mapped
381  *
382  * Use the idmapping of @mnt_userns to remap a @kgid into @fs_userns. Use this
383  * function when preparing a @kgid to be written to disk or inode.
384  *
385  * If no_idmapping() determines that this is not an idmapped mount we can
386  * simply return @kgid unchanged.
387  * If initial_idmapping() tells us that the filesystem is not mounted with an
388  * idmapping we know the value of @kgid won't change when calling
389  * make_kgid() so we can simply retrieve the value via KGIDT_INIT()
390  * directly.
391  *
392  * Return: @kgid mapped according to @mnt_userns.
393  * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
394  * returned.
395  */
mapped_kgid_user(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,kgid_t kgid)396 static inline kgid_t mapped_kgid_user(struct user_namespace *mnt_userns,
397 				      struct user_namespace *fs_userns,
398 				      kgid_t kgid)
399 {
400 	return from_vfsgid(mnt_userns, fs_userns, VFSGIDT_INIT(kgid));
401 }
402 
403 /**
404  * vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
405  * @mnt_userns: the mount's idmapping
406  * @fs_userns: the filesystem's idmapping
407  * @vfsgid: vfsgid to be mapped
408  *
409  * Check whether @vfsgid has a mapping in the filesystem idmapping. Use this
410  * function to check whether the filesystem idmapping has a mapping for
411  * @vfsgid.
412  *
413  * Return: true if @vfsgid has a mapping in the filesystem, false if not.
414  */
vfsgid_has_fsmapping(struct user_namespace * mnt_userns,struct user_namespace * fs_userns,vfsgid_t vfsgid)415 static inline bool vfsgid_has_fsmapping(struct user_namespace *mnt_userns,
416 					struct user_namespace *fs_userns,
417 					vfsgid_t vfsgid)
418 {
419 	return gid_valid(from_vfsgid(mnt_userns, fs_userns, vfsgid));
420 }
421 
422 /**
423  * vfsgid_into_kgid - convert vfsgid into kgid
424  * @vfsgid: the vfsgid to convert
425  *
426  * This can be used when a vfsgid is committed as a kgid.
427  *
428  * Return: a kgid with the value of @vfsgid
429  */
vfsgid_into_kgid(vfsgid_t vfsgid)430 static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
431 {
432 	return AS_KGIDT(vfsgid);
433 }
434 
435 /**
436  * mapped_fsuid - return caller's fsuid mapped up into a mnt_userns
437  * @mnt_userns: the mount's idmapping
438  * @fs_userns: the filesystem's idmapping
439  *
440  * Use this helper to initialize a new vfs or filesystem object based on
441  * the caller's fsuid. A common example is initializing the i_uid field of
442  * a newly allocated inode triggered by a creation event such as mkdir or
443  * O_CREAT. Other examples include the allocation of quotas for a specific
444  * user.
445  *
446  * Return: the caller's current fsuid mapped up according to @mnt_userns.
447  */
mapped_fsuid(struct user_namespace * mnt_userns,struct user_namespace * fs_userns)448 static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns,
449 				  struct user_namespace *fs_userns)
450 {
451 	return from_vfsuid(mnt_userns, fs_userns,
452 			   VFSUIDT_INIT(current_fsuid()));
453 }
454 
455 /**
456  * mapped_fsgid - return caller's fsgid mapped up into a mnt_userns
457  * @mnt_userns: the mount's idmapping
458  * @fs_userns: the filesystem's idmapping
459  *
460  * Use this helper to initialize a new vfs or filesystem object based on
461  * the caller's fsgid. A common example is initializing the i_gid field of
462  * a newly allocated inode triggered by a creation event such as mkdir or
463  * O_CREAT. Other examples include the allocation of quotas for a specific
464  * user.
465  *
466  * Return: the caller's current fsgid mapped up according to @mnt_userns.
467  */
mapped_fsgid(struct user_namespace * mnt_userns,struct user_namespace * fs_userns)468 static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns,
469 				  struct user_namespace *fs_userns)
470 {
471 	return from_vfsgid(mnt_userns, fs_userns,
472 			   VFSGIDT_INIT(current_fsgid()));
473 }
474 
475 #endif /* _LINUX_MNT_IDMAPPING_H */
476