include/linux/mnt_idmapping.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef _LINUX_MNT_IDMAPPING_H
0003 #define _LINUX_MNT_IDMAPPING_H
0004
0005 #include <linux/types.h>
0006 #include <linux/uidgid.h>
0007
0008 struct user_namespace;
0009 /*
0010  * Carries the initial idmapping of 0:0:4294967295 which is an identity
0011  * mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
0012  * mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
0013  */
0014 extern struct user_namespace init_user_ns;
0015
0016 typedef struct {
0017     uid_t val;
0018 } vfsuid_t;
0019
0020 typedef struct {
0021     gid_t val;
0022 } vfsgid_t;
0023
0024 static_assert(sizeof(vfsuid_t) == sizeof(kuid_t));
0025 static_assert(sizeof(vfsgid_t) == sizeof(kgid_t));
0026 static_assert(offsetof(vfsuid_t, val) == offsetof(kuid_t, val));
0027 static_assert(offsetof(vfsgid_t, val) == offsetof(kgid_t, val));
0028
0029 #ifdef CONFIG_MULTIUSER
0030 static inline uid_t __vfsuid_val(vfsuid_t uid)
0031 {
0032     return uid.val;
0033 }
0034
0035 static inline gid_t __vfsgid_val(vfsgid_t gid)
0036 {
0037     return gid.val;
0038 }
0039 #else
0040 static inline uid_t __vfsuid_val(vfsuid_t uid)
0041 {
0042     return 0;
0043 }
0044
0045 static inline gid_t __vfsgid_val(vfsgid_t gid)
0046 {
0047     return 0;
0048 }
0049 #endif
0050
0051 static inline bool vfsuid_valid(vfsuid_t uid)
0052 {
0053     return __vfsuid_val(uid) != (uid_t)-1;
0054 }
0055
0056 static inline bool vfsgid_valid(vfsgid_t gid)
0057 {
0058     return __vfsgid_val(gid) != (gid_t)-1;
0059 }
0060
0061 static inline bool vfsuid_eq(vfsuid_t left, vfsuid_t right)
0062 {
0063     return vfsuid_valid(left) && __vfsuid_val(left) == __vfsuid_val(right);
0064 }
0065
0066 static inline bool vfsgid_eq(vfsgid_t left, vfsgid_t right)
0067 {
0068     return vfsgid_valid(left) && __vfsgid_val(left) == __vfsgid_val(right);
0069 }
0070
0071 /**
0072  * vfsuid_eq_kuid - check whether kuid and vfsuid have the same value
0073  * @vfsuid: the vfsuid to compare
0074  * @kuid: the kuid to compare
0075  *
0076  * Check whether @vfsuid and @kuid have the same values.
0077  *
0078  * Return: true if @vfsuid and @kuid have the same value, false if not.
0079  * Comparison between two invalid uids returns false.
0080  */
0081 static inline bool vfsuid_eq_kuid(vfsuid_t vfsuid, kuid_t kuid)
0082 {
0083     return vfsuid_valid(vfsuid) && __vfsuid_val(vfsuid) == __kuid_val(kuid);
0084 }
0085
0086 /**
0087  * vfsgid_eq_kgid - check whether kgid and vfsgid have the same value
0088  * @vfsgid: the vfsgid to compare
0089  * @kgid: the kgid to compare
0090  *
0091  * Check whether @vfsgid and @kgid have the same values.
0092  *
0093  * Return: true if @vfsgid and @kgid have the same value, false if not.
0094  * Comparison between two invalid gids returns false.
0095  */
0096 static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t kgid)
0097 {
0098     return vfsgid_valid(vfsgid) && __vfsgid_val(vfsgid) == __kgid_val(kgid);
0099 }
0100
0101 /*
0102  * vfs{g,u}ids are created from k{g,u}ids.
0103  * We don't allow them to be created from regular {u,g}id.
0104  */
0105 #define VFSUIDT_INIT(val) (vfsuid_t){ __kuid_val(val) }
0106 #define VFSGIDT_INIT(val) (vfsgid_t){ __kgid_val(val) }
0107
0108 #define INVALID_VFSUID VFSUIDT_INIT(INVALID_UID)
0109 #define INVALID_VFSGID VFSGIDT_INIT(INVALID_GID)
0110
0111 /*
0112  * Allow a vfs{g,u}id to be used as a k{g,u}id where we want to compare
0113  * whether the mapped value is identical to value of a k{g,u}id.
0114  */
0115 #define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) }
0116 #define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) }
0117
0118 #ifdef CONFIG_MULTIUSER
0119 /**
0120  * vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups
0121  * @vfsgid: the mnt gid to match
0122  *
0123  * This function can be used to determine whether @vfsuid matches any of the
0124  * caller's groups.
0125  *
0126  * Return: 1 if vfsuid matches caller's groups, 0 if not.
0127  */
0128 static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
0129 {
0130     return in_group_p(AS_KGIDT(vfsgid));
0131 }
0132 #else
0133 static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
0134 {
0135     return 1;
0136 }
0137 #endif
0138
0139 /**
0140  * initial_idmapping - check whether this is the initial mapping
0141  * @ns: idmapping to check
0142  *
0143  * Check whether this is the initial mapping, mapping 0 to 0, 1 to 1,
0144  * [...], 1000 to 1000 [...].
0145  *
0146  * Return: true if this is the initial mapping, false if not.
0147  */
0148 static inline bool initial_idmapping(const struct user_namespace *ns)
0149 {
0150     return ns == &init_user_ns;
0151 }
0152
0153 /**
0154  * no_idmapping - check whether we can skip remapping a kuid/gid
0155  * @mnt_userns: the mount's idmapping
0156  * @fs_userns: the filesystem's idmapping
0157  *
0158  * This function can be used to check whether a remapping between two
0159  * idmappings is required.
0160  * An idmapped mount is a mount that has an idmapping attached to it that
0161  * is different from the filsystem's idmapping and the initial idmapping.
0162  * If the initial mapping is used or the idmapping of the mount and the
0163  * filesystem are identical no remapping is required.
0164  *
0165  * Return: true if remapping can be skipped, false if not.
0166  */
0167 static inline bool no_idmapping(const struct user_namespace *mnt_userns,
0168                 const struct user_namespace *fs_userns)
0169 {
0170     return initial_idmapping(mnt_userns) || mnt_userns == fs_userns;
0171 }
0172
0173 /**
0174  * make_vfsuid - map a filesystem kuid into a mnt_userns
0175  * @mnt_userns: the mount's idmapping
0176  * @fs_userns: the filesystem's idmapping
0177  * @kuid : kuid to be mapped
0178  *
0179  * Take a @kuid and remap it from @fs_userns into @mnt_userns. Use this
0180  * function when preparing a @kuid to be reported to userspace.
0181  *
0182  * If no_idmapping() determines that this is not an idmapped mount we can
0183  * simply return @kuid unchanged.
0184  * If initial_idmapping() tells us that the filesystem is not mounted with an
0185  * idmapping we know the value of @kuid won't change when calling
0186  * from_kuid() so we can simply retrieve the value via __kuid_val()
0187  * directly.
0188  *
0189  * Return: @kuid mapped according to @mnt_userns.
0190  * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
0191  * returned.
0192  */
0193
0194 static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
0195                    struct user_namespace *fs_userns,
0196                    kuid_t kuid)
0197 {
0198     uid_t uid;
0199
0200     if (no_idmapping(mnt_userns, fs_userns))
0201         return VFSUIDT_INIT(kuid);
0202     if (initial_idmapping(fs_userns))
0203         uid = __kuid_val(kuid);
0204     else
0205         uid = from_kuid(fs_userns, kuid);
0206     if (uid == (uid_t)-1)
0207         return INVALID_VFSUID;
0208     return VFSUIDT_INIT(make_kuid(mnt_userns, uid));
0209 }
0210
0211 static inline kuid_t mapped_kuid_fs(struct user_namespace *mnt_userns,
0212                     struct user_namespace *fs_userns,
0213                     kuid_t kuid)
0214 {
0215     return AS_KUIDT(make_vfsuid(mnt_userns, fs_userns, kuid));
0216 }
0217
0218 /**
0219  * make_vfsgid - map a filesystem kgid into a mnt_userns
0220  * @mnt_userns: the mount's idmapping
0221  * @fs_userns: the filesystem's idmapping
0222  * @kgid : kgid to be mapped
0223  *
0224  * Take a @kgid and remap it from @fs_userns into @mnt_userns. Use this
0225  * function when preparing a @kgid to be reported to userspace.
0226  *
0227  * If no_idmapping() determines that this is not an idmapped mount we can
0228  * simply return @kgid unchanged.
0229  * If initial_idmapping() tells us that the filesystem is not mounted with an
0230  * idmapping we know the value of @kgid won't change when calling
0231  * from_kgid() so we can simply retrieve the value via __kgid_val()
0232  * directly.
0233  *
0234  * Return: @kgid mapped according to @mnt_userns.
0235  * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
0236  * returned.
0237  */
0238
0239 static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
0240                    struct user_namespace *fs_userns,
0241                    kgid_t kgid)
0242 {
0243     gid_t gid;
0244
0245     if (no_idmapping(mnt_userns, fs_userns))
0246         return VFSGIDT_INIT(kgid);
0247     if (initial_idmapping(fs_userns))
0248         gid = __kgid_val(kgid);
0249     else
0250         gid = from_kgid(fs_userns, kgid);
0251     if (gid == (gid_t)-1)
0252         return INVALID_VFSGID;
0253     return VFSGIDT_INIT(make_kgid(mnt_userns, gid));
0254 }
0255
0256 static inline kgid_t mapped_kgid_fs(struct user_namespace *mnt_userns,
0257                     struct user_namespace *fs_userns,
0258                     kgid_t kgid)
0259 {
0260     return AS_KGIDT(make_vfsgid(mnt_userns, fs_userns, kgid));
0261 }
0262
0263 /**
0264  * from_vfsuid - map a vfsuid into the filesystem idmapping
0265  * @mnt_userns: the mount's idmapping
0266  * @fs_userns: the filesystem's idmapping
0267  * @vfsuid : vfsuid to be mapped
0268  *
0269  * Map @vfsuid into the filesystem idmapping. This function has to be used in
0270  * order to e.g. write @vfsuid to inode->i_uid.
0271  *
0272  * Return: @vfsuid mapped into the filesystem idmapping
0273  */
0274 static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
0275                  struct user_namespace *fs_userns,
0276                  vfsuid_t vfsuid)
0277 {
0278     uid_t uid;
0279
0280     if (no_idmapping(mnt_userns, fs_userns))
0281         return AS_KUIDT(vfsuid);
0282     uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
0283     if (uid == (uid_t)-1)
0284         return INVALID_UID;
0285     if (initial_idmapping(fs_userns))
0286         return KUIDT_INIT(uid);
0287     return make_kuid(fs_userns, uid);
0288 }
0289
0290 /**
0291  * mapped_kuid_user - map a user kuid into a mnt_userns
0292  * @mnt_userns: the mount's idmapping
0293  * @fs_userns: the filesystem's idmapping
0294  * @kuid : kuid to be mapped
0295  *
0296  * Use the idmapping of @mnt_userns to remap a @kuid into @fs_userns. Use this
0297  * function when preparing a @kuid to be written to disk or inode.
0298  *
0299  * If no_idmapping() determines that this is not an idmapped mount we can
0300  * simply return @kuid unchanged.
0301  * If initial_idmapping() tells us that the filesystem is not mounted with an
0302  * idmapping we know the value of @kuid won't change when calling
0303  * make_kuid() so we can simply retrieve the value via KUIDT_INIT()
0304  * directly.
0305  *
0306  * Return: @kuid mapped according to @mnt_userns.
0307  * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
0308  * returned.
0309  */
0310 static inline kuid_t mapped_kuid_user(struct user_namespace *mnt_userns,
0311                       struct user_namespace *fs_userns,
0312                       kuid_t kuid)
0313 {
0314     return from_vfsuid(mnt_userns, fs_userns, VFSUIDT_INIT(kuid));
0315 }
0316
0317 /**
0318  * vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
0319  * @mnt_userns: the mount's idmapping
0320  * @fs_userns: the filesystem's idmapping
0321  * @vfsuid: vfsuid to be mapped
0322  *
0323  * Check whether @vfsuid has a mapping in the filesystem idmapping. Use this
0324  * function to check whether the filesystem idmapping has a mapping for
0325  * @vfsuid.
0326  *
0327  * Return: true if @vfsuid has a mapping in the filesystem, false if not.
0328  */
0329 static inline bool vfsuid_has_fsmapping(struct user_namespace *mnt_userns,
0330                     struct user_namespace *fs_userns,
0331                     vfsuid_t vfsuid)
0332 {
0333     return uid_valid(from_vfsuid(mnt_userns, fs_userns, vfsuid));
0334 }
0335
0336 /**
0337  * vfsuid_into_kuid - convert vfsuid into kuid
0338  * @vfsuid: the vfsuid to convert
0339  *
0340  * This can be used when a vfsuid is committed as a kuid.
0341  *
0342  * Return: a kuid with the value of @vfsuid
0343  */
0344 static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
0345 {
0346     return AS_KUIDT(vfsuid);
0347 }
0348
0349 /**
0350  * from_vfsgid - map a vfsgid into the filesystem idmapping
0351  * @mnt_userns: the mount's idmapping
0352  * @fs_userns: the filesystem's idmapping
0353  * @vfsgid : vfsgid to be mapped
0354  *
0355  * Map @vfsgid into the filesystem idmapping. This function has to be used in
0356  * order to e.g. write @vfsgid to inode->i_gid.
0357  *
0358  * Return: @vfsgid mapped into the filesystem idmapping
0359  */
0360 static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
0361                  struct user_namespace *fs_userns,
0362                  vfsgid_t vfsgid)
0363 {
0364     gid_t gid;
0365
0366     if (no_idmapping(mnt_userns, fs_userns))
0367         return AS_KGIDT(vfsgid);
0368     gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
0369     if (gid == (gid_t)-1)
0370         return INVALID_GID;
0371     if (initial_idmapping(fs_userns))
0372         return KGIDT_INIT(gid);
0373     return make_kgid(fs_userns, gid);
0374 }
0375
0376 /**
0377  * mapped_kgid_user - map a user kgid into a mnt_userns
0378  * @mnt_userns: the mount's idmapping
0379  * @fs_userns: the filesystem's idmapping
0380  * @kgid : kgid to be mapped
0381  *
0382  * Use the idmapping of @mnt_userns to remap a @kgid into @fs_userns. Use this
0383  * function when preparing a @kgid to be written to disk or inode.
0384  *
0385  * If no_idmapping() determines that this is not an idmapped mount we can
0386  * simply return @kgid unchanged.
0387  * If initial_idmapping() tells us that the filesystem is not mounted with an
0388  * idmapping we know the value of @kgid won't change when calling
0389  * make_kgid() so we can simply retrieve the value via KGIDT_INIT()
0390  * directly.
0391  *
0392  * Return: @kgid mapped according to @mnt_userns.
0393  * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
0394  * returned.
0395  */
0396 static inline kgid_t mapped_kgid_user(struct user_namespace *mnt_userns,
0397                       struct user_namespace *fs_userns,
0398                       kgid_t kgid)
0399 {
0400     return from_vfsgid(mnt_userns, fs_userns, VFSGIDT_INIT(kgid));
0401 }
0402
0403 /**
0404  * vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
0405  * @mnt_userns: the mount's idmapping
0406  * @fs_userns: the filesystem's idmapping
0407  * @vfsgid: vfsgid to be mapped
0408  *
0409  * Check whether @vfsgid has a mapping in the filesystem idmapping. Use this
0410  * function to check whether the filesystem idmapping has a mapping for
0411  * @vfsgid.
0412  *
0413  * Return: true if @vfsgid has a mapping in the filesystem, false if not.
0414  */
0415 static inline bool vfsgid_has_fsmapping(struct user_namespace *mnt_userns,
0416                     struct user_namespace *fs_userns,
0417                     vfsgid_t vfsgid)
0418 {
0419     return gid_valid(from_vfsgid(mnt_userns, fs_userns, vfsgid));
0420 }
0421
0422 /**
0423  * vfsgid_into_kgid - convert vfsgid into kgid
0424  * @vfsgid: the vfsgid to convert
0425  *
0426  * This can be used when a vfsgid is committed as a kgid.
0427  *
0428  * Return: a kgid with the value of @vfsgid
0429  */
0430 static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
0431 {
0432     return AS_KGIDT(vfsgid);
0433 }
0434
0435 /**
0436  * mapped_fsuid - return caller's fsuid mapped up into a mnt_userns
0437  * @mnt_userns: the mount's idmapping
0438  * @fs_userns: the filesystem's idmapping
0439  *
0440  * Use this helper to initialize a new vfs or filesystem object based on
0441  * the caller's fsuid. A common example is initializing the i_uid field of
0442  * a newly allocated inode triggered by a creation event such as mkdir or
0443  * O_CREAT. Other examples include the allocation of quotas for a specific
0444  * user.
0445  *
0446  * Return: the caller's current fsuid mapped up according to @mnt_userns.
0447  */
0448 static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns,
0449                   struct user_namespace *fs_userns)
0450 {
0451     return from_vfsuid(mnt_userns, fs_userns,
0452                VFSUIDT_INIT(current_fsuid()));
0453 }
0454
0455 /**
0456  * mapped_fsgid - return caller's fsgid mapped up into a mnt_userns
0457  * @mnt_userns: the mount's idmapping
0458  * @fs_userns: the filesystem's idmapping
0459  *
0460  * Use this helper to initialize a new vfs or filesystem object based on
0461  * the caller's fsgid. A common example is initializing the i_gid field of
0462  * a newly allocated inode triggered by a creation event such as mkdir or
0463  * O_CREAT. Other examples include the allocation of quotas for a specific
0464  * user.
0465  *
0466  * Return: the caller's current fsgid mapped up according to @mnt_userns.
0467  */
0468 static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns,
0469                   struct user_namespace *fs_userns)
0470 {
0471     return from_vfsgid(mnt_userns, fs_userns,
0472                VFSGIDT_INIT(current_fsgid()));
0473 }
0474
0475 #endif /* _LINUX_MNT_IDMAPPING_H */