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