include/linux/mnt_idmapping.h - kernel/common - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_MNT_IDMAPPING_H
 #define _LINUX_MNT_IDMAPPING_H

 #include <linux/types.h>
 #include <linux/uidgid.h>

 struct user_namespace;
 /*
  * Carries the initial idmapping of 0:0:4294967295 which is an identity
  * mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
  * mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
  */
 extern struct user_namespace init_user_ns;

 typedef struct {
 	uid_t val;
 } vfsuid_t;

 typedef struct {
 	gid_t val;
 } vfsgid_t;

 static_assert(sizeof(vfsuid_t) == sizeof(kuid_t));
 static_assert(sizeof(vfsgid_t) == sizeof(kgid_t));
 static_assert(offsetof(vfsuid_t, val) == offsetof(kuid_t, val));
 static_assert(offsetof(vfsgid_t, val) == offsetof(kgid_t, val));

 #ifdef CONFIG_MULTIUSER
 static inline uid_t __vfsuid_val(vfsuid_t uid)
 {
 	return uid.val;
 }

 static inline gid_t __vfsgid_val(vfsgid_t gid)
 {
 	return gid.val;
 }
 #else
 static inline uid_t __vfsuid_val(vfsuid_t uid)
 {
 	return 0;
 }

 static inline gid_t __vfsgid_val(vfsgid_t gid)
 {
 	return 0;
 }
 #endif

 static inline bool vfsuid_valid(vfsuid_t uid)
 {
 	return __vfsuid_val(uid) != (uid_t)-1;
 }

 static inline bool vfsgid_valid(vfsgid_t gid)
 {
 	return __vfsgid_val(gid) != (gid_t)-1;
 }

 static inline bool vfsuid_eq(vfsuid_t left, vfsuid_t right)
 {
 	return vfsuid_valid(left) && __vfsuid_val(left) == __vfsuid_val(right);
 }

 static inline bool vfsgid_eq(vfsgid_t left, vfsgid_t right)
 {
 	return vfsgid_valid(left) && __vfsgid_val(left) == __vfsgid_val(right);
 }

 /**
  * vfsuid_eq_kuid - check whether kuid and vfsuid have the same value
  * @vfsuid: the vfsuid to compare
  * @kuid: the kuid to compare
  *
  * Check whether @vfsuid and @kuid have the same values.
  *
  * Return: true if @vfsuid and @kuid have the same value, false if not.
  * Comparison between two invalid uids returns false.
  */
 static inline bool vfsuid_eq_kuid(vfsuid_t vfsuid, kuid_t kuid)
 {
 	return vfsuid_valid(vfsuid) && __vfsuid_val(vfsuid) == __kuid_val(kuid);
 }

 /**
  * vfsgid_eq_kgid - check whether kgid and vfsgid have the same value
  * @vfsgid: the vfsgid to compare
  * @kgid: the kgid to compare
  *
  * Check whether @vfsgid and @kgid have the same values.
  *
  * Return: true if @vfsgid and @kgid have the same value, false if not.
  * Comparison between two invalid gids returns false.
  */
 static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t kgid)
 {
 	return vfsgid_valid(vfsgid) && __vfsgid_val(vfsgid) == __kgid_val(kgid);
 }

 /*
  * vfs{g,u}ids are created from k{g,u}ids.
  * We don't allow them to be created from regular {u,g}id.
  */
 #define VFSUIDT_INIT(val) (vfsuid_t){ __kuid_val(val) }
 #define VFSGIDT_INIT(val) (vfsgid_t){ __kgid_val(val) }

 #define INVALID_VFSUID VFSUIDT_INIT(INVALID_UID)
 #define INVALID_VFSGID VFSGIDT_INIT(INVALID_GID)

 /*
  * Allow a vfs{g,u}id to be used as a k{g,u}id where we want to compare
  * whether the mapped value is identical to value of a k{g,u}id.
  */
 #define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) }
 #define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) }

 #ifdef CONFIG_MULTIUSER
 /**
  * vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups
  * @vfsgid: the mnt gid to match
  *
  * This function can be used to determine whether @vfsuid matches any of the
  * caller's groups.
  *
  * Return: 1 if vfsuid matches caller's groups, 0 if not.
  */
 static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
 {
 	return in_group_p(AS_KGIDT(vfsgid));
 }
 #else
 static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
 {
 	return 1;
 }
 #endif

 /**
  * initial_idmapping - check whether this is the initial mapping
  * @ns: idmapping to check
  *
  * Check whether this is the initial mapping, mapping 0 to 0, 1 to 1,
  * [...], 1000 to 1000 [...].
  *
  * Return: true if this is the initial mapping, false if not.
  */
 static inline bool initial_idmapping(const struct user_namespace *ns)
 {
 	return ns == &init_user_ns;
 }

 /**
  * no_idmapping - check whether we can skip remapping a kuid/gid
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  *
  * This function can be used to check whether a remapping between two
  * idmappings is required.
  * An idmapped mount is a mount that has an idmapping attached to it that
  * is different from the filsystem's idmapping and the initial idmapping.
  * If the initial mapping is used or the idmapping of the mount and the
  * filesystem are identical no remapping is required.
  *
  * Return: true if remapping can be skipped, false if not.
  */
 static inline bool no_idmapping(const struct user_namespace *mnt_userns,
 				const struct user_namespace *fs_userns)
 {
 	return initial_idmapping(mnt_userns) || mnt_userns == fs_userns;
 }

 /**
  * make_vfsuid - map a filesystem kuid into a mnt_userns
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @kuid : kuid to be mapped
  *
  * Take a @kuid and remap it from @fs_userns into @mnt_userns. Use this
  * function when preparing a @kuid to be reported to userspace.
  *
  * If no_idmapping() determines that this is not an idmapped mount we can
  * simply return @kuid unchanged.
  * If initial_idmapping() tells us that the filesystem is not mounted with an
  * idmapping we know the value of @kuid won't change when calling
  * from_kuid() so we can simply retrieve the value via __kuid_val()
  * directly.
  *
  * Return: @kuid mapped according to @mnt_userns.
  * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
  * returned.
  */

 static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
 				   struct user_namespace *fs_userns,
 				   kuid_t kuid)
 {
 	uid_t uid;

 	if (no_idmapping(mnt_userns, fs_userns))
 		return VFSUIDT_INIT(kuid);
 	if (initial_idmapping(fs_userns))
 		uid = __kuid_val(kuid);
 	else
 		uid = from_kuid(fs_userns, kuid);
 	if (uid == (uid_t)-1)
 		return INVALID_VFSUID;
 	return VFSUIDT_INIT(make_kuid(mnt_userns, uid));
 }

 static inline kuid_t mapped_kuid_fs(struct user_namespace *mnt_userns,
 				    struct user_namespace *fs_userns,
 				    kuid_t kuid)
 {
 	return AS_KUIDT(make_vfsuid(mnt_userns, fs_userns, kuid));
 }

 /**
  * make_vfsgid - map a filesystem kgid into a mnt_userns
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @kgid : kgid to be mapped
  *
  * Take a @kgid and remap it from @fs_userns into @mnt_userns. Use this
  * function when preparing a @kgid to be reported to userspace.
  *
  * If no_idmapping() determines that this is not an idmapped mount we can
  * simply return @kgid unchanged.
  * If initial_idmapping() tells us that the filesystem is not mounted with an
  * idmapping we know the value of @kgid won't change when calling
  * from_kgid() so we can simply retrieve the value via __kgid_val()
  * directly.
  *
  * Return: @kgid mapped according to @mnt_userns.
  * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
  * returned.
  */

 static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
 				   struct user_namespace *fs_userns,
 				   kgid_t kgid)
 {
 	gid_t gid;

 	if (no_idmapping(mnt_userns, fs_userns))
 		return VFSGIDT_INIT(kgid);
 	if (initial_idmapping(fs_userns))
 		gid = __kgid_val(kgid);
 	else
 		gid = from_kgid(fs_userns, kgid);
 	if (gid == (gid_t)-1)
 		return INVALID_VFSGID;
 	return VFSGIDT_INIT(make_kgid(mnt_userns, gid));
 }

 static inline kgid_t mapped_kgid_fs(struct user_namespace *mnt_userns,
 				    struct user_namespace *fs_userns,
 				    kgid_t kgid)
 {
 	return AS_KGIDT(make_vfsgid(mnt_userns, fs_userns, kgid));
 }

 /**
  * from_vfsuid - map a vfsuid into the filesystem idmapping
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsuid : vfsuid to be mapped
  *
  * Map @vfsuid into the filesystem idmapping. This function has to be used in
  * order to e.g. write @vfsuid to inode->i_uid.
  *
  * Return: @vfsuid mapped into the filesystem idmapping
  */
 static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
 				 struct user_namespace *fs_userns,
 				 vfsuid_t vfsuid)
 {
 	uid_t uid;

 	if (no_idmapping(mnt_userns, fs_userns))
 		return AS_KUIDT(vfsuid);
 	uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
 	if (uid == (uid_t)-1)
 		return INVALID_UID;
 	if (initial_idmapping(fs_userns))
 		return KUIDT_INIT(uid);
 	return make_kuid(fs_userns, uid);
 }

 /**
  * mapped_kuid_user - map a user kuid into a mnt_userns
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @kuid : kuid to be mapped
  *
  * Use the idmapping of @mnt_userns to remap a @kuid into @fs_userns. Use this
  * function when preparing a @kuid to be written to disk or inode.
  *
  * If no_idmapping() determines that this is not an idmapped mount we can
  * simply return @kuid unchanged.
  * If initial_idmapping() tells us that the filesystem is not mounted with an
  * idmapping we know the value of @kuid won't change when calling
  * make_kuid() so we can simply retrieve the value via KUIDT_INIT()
  * directly.
  *
  * Return: @kuid mapped according to @mnt_userns.
  * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
  * returned.
  */
 static inline kuid_t mapped_kuid_user(struct user_namespace *mnt_userns,
 				      struct user_namespace *fs_userns,
 				      kuid_t kuid)
 {
 	return from_vfsuid(mnt_userns, fs_userns, VFSUIDT_INIT(kuid));
 }

 /**
  * vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsuid: vfsuid to be mapped
  *
  * Check whether @vfsuid has a mapping in the filesystem idmapping. Use this
  * function to check whether the filesystem idmapping has a mapping for
  * @vfsuid.
  *
  * Return: true if @vfsuid has a mapping in the filesystem, false if not.
  */
 static inline bool vfsuid_has_fsmapping(struct user_namespace *mnt_userns,
 					struct user_namespace *fs_userns,
 					vfsuid_t vfsuid)
 {
 	return uid_valid(from_vfsuid(mnt_userns, fs_userns, vfsuid));
 }

 /**
  * vfsuid_into_kuid - convert vfsuid into kuid
  * @vfsuid: the vfsuid to convert
  *
  * This can be used when a vfsuid is committed as a kuid.
  *
  * Return: a kuid with the value of @vfsuid
  */
 static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
 {
 	return AS_KUIDT(vfsuid);
 }

 /**
  * from_vfsgid - map a vfsgid into the filesystem idmapping
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsgid : vfsgid to be mapped
  *
  * Map @vfsgid into the filesystem idmapping. This function has to be used in
  * order to e.g. write @vfsgid to inode->i_gid.
  *
  * Return: @vfsgid mapped into the filesystem idmapping
  */
 static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
 				 struct user_namespace *fs_userns,
 				 vfsgid_t vfsgid)
 {
 	gid_t gid;

 	if (no_idmapping(mnt_userns, fs_userns))
 		return AS_KGIDT(vfsgid);
 	gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
 	if (gid == (gid_t)-1)
 		return INVALID_GID;
 	if (initial_idmapping(fs_userns))
 		return KGIDT_INIT(gid);
 	return make_kgid(fs_userns, gid);
 }

 /**
  * mapped_kgid_user - map a user kgid into a mnt_userns
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @kgid : kgid to be mapped
  *
  * Use the idmapping of @mnt_userns to remap a @kgid into @fs_userns. Use this
  * function when preparing a @kgid to be written to disk or inode.
  *
  * If no_idmapping() determines that this is not an idmapped mount we can
  * simply return @kgid unchanged.
  * If initial_idmapping() tells us that the filesystem is not mounted with an
  * idmapping we know the value of @kgid won't change when calling
  * make_kgid() so we can simply retrieve the value via KGIDT_INIT()
  * directly.
  *
  * Return: @kgid mapped according to @mnt_userns.
  * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
  * returned.
  */
 static inline kgid_t mapped_kgid_user(struct user_namespace *mnt_userns,
 				      struct user_namespace *fs_userns,
 				      kgid_t kgid)
 {
 	return from_vfsgid(mnt_userns, fs_userns, VFSGIDT_INIT(kgid));
 }

 /**
  * vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsgid: vfsgid to be mapped
  *
  * Check whether @vfsgid has a mapping in the filesystem idmapping. Use this
  * function to check whether the filesystem idmapping has a mapping for
  * @vfsgid.
  *
  * Return: true if @vfsgid has a mapping in the filesystem, false if not.
  */
 static inline bool vfsgid_has_fsmapping(struct user_namespace *mnt_userns,
 					struct user_namespace *fs_userns,
 					vfsgid_t vfsgid)
 {
 	return gid_valid(from_vfsgid(mnt_userns, fs_userns, vfsgid));
 }

 /**
  * vfsgid_into_kgid - convert vfsgid into kgid
  * @vfsgid: the vfsgid to convert
  *
  * This can be used when a vfsgid is committed as a kgid.
  *
  * Return: a kgid with the value of @vfsgid
  */
 static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
 {
 	return AS_KGIDT(vfsgid);
 }

 /**
  * mapped_fsuid - return caller's fsuid mapped up into a mnt_userns
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  *
  * Use this helper to initialize a new vfs or filesystem object based on
  * the caller's fsuid. A common example is initializing the i_uid field of
  * a newly allocated inode triggered by a creation event such as mkdir or
  * O_CREAT. Other examples include the allocation of quotas for a specific
  * user.
  *
  * Return: the caller's current fsuid mapped up according to @mnt_userns.
  */
 static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns,
 				  struct user_namespace *fs_userns)
 {
 	return from_vfsuid(mnt_userns, fs_userns,
 			   VFSUIDT_INIT(current_fsuid()));
 }

 /**
  * mapped_fsgid - return caller's fsgid mapped up into a mnt_userns
  * @mnt_userns: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  *
  * Use this helper to initialize a new vfs or filesystem object based on
  * the caller's fsgid. A common example is initializing the i_gid field of
  * a newly allocated inode triggered by a creation event such as mkdir or
  * O_CREAT. Other examples include the allocation of quotas for a specific
  * user.
  *
  * Return: the caller's current fsgid mapped up according to @mnt_userns.
  */
 static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns,
 				  struct user_namespace *fs_userns)
 {
 	return from_vfsgid(mnt_userns, fs_userns,
 			   VFSGIDT_INIT(current_fsgid()));
 }

 #endif /* _LINUX_MNT_IDMAPPING_H */
	/* SPDX-License-Identifier: GPL-2.0 */
	#ifndef _LINUX_MNT_IDMAPPING_H
	#define _LINUX_MNT_IDMAPPING_H

	#include <linux/types.h>
	#include <linux/uidgid.h>

	struct user_namespace;
	/*
	* Carries the initial idmapping of 0:0:4294967295 which is an identity
	* mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
	* mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
	*/
	extern struct user_namespace init_user_ns;

	typedef struct {
	uid_t val;
	} vfsuid_t;

	typedef struct {
	gid_t val;
	} vfsgid_t;

	static_assert(sizeof(vfsuid_t) == sizeof(kuid_t));
	static_assert(sizeof(vfsgid_t) == sizeof(kgid_t));
	static_assert(offsetof(vfsuid_t, val) == offsetof(kuid_t, val));
	static_assert(offsetof(vfsgid_t, val) == offsetof(kgid_t, val));

	#ifdef CONFIG_MULTIUSER
	static inline uid_t __vfsuid_val(vfsuid_t uid)
	{
	return uid.val;
	}

	static inline gid_t __vfsgid_val(vfsgid_t gid)
	{
	return gid.val;
	}
	#else
	static inline uid_t __vfsuid_val(vfsuid_t uid)
	{
	return 0;
	}

	static inline gid_t __vfsgid_val(vfsgid_t gid)
	{
	return 0;
	}
	#endif

	static inline bool vfsuid_valid(vfsuid_t uid)
	{
	return __vfsuid_val(uid) != (uid_t)-1;
	}

	static inline bool vfsgid_valid(vfsgid_t gid)
	{
	return __vfsgid_val(gid) != (gid_t)-1;
	}

	static inline bool vfsuid_eq(vfsuid_t left, vfsuid_t right)
	{
	return vfsuid_valid(left) && __vfsuid_val(left) == __vfsuid_val(right);
	}

	static inline bool vfsgid_eq(vfsgid_t left, vfsgid_t right)
	{
	return vfsgid_valid(left) && __vfsgid_val(left) == __vfsgid_val(right);
	}

	/**
	* vfsuid_eq_kuid - check whether kuid and vfsuid have the same value
	* @vfsuid: the vfsuid to compare
	* @kuid: the kuid to compare
	*
	* Check whether @vfsuid and @kuid have the same values.
	*
	* Return: true if @vfsuid and @kuid have the same value, false if not.
	* Comparison between two invalid uids returns false.
	*/
	static inline bool vfsuid_eq_kuid(vfsuid_t vfsuid, kuid_t kuid)
	{
	return vfsuid_valid(vfsuid) && __vfsuid_val(vfsuid) == __kuid_val(kuid);
	}

	/**
	* vfsgid_eq_kgid - check whether kgid and vfsgid have the same value
	* @vfsgid: the vfsgid to compare
	* @kgid: the kgid to compare
	*
	* Check whether @vfsgid and @kgid have the same values.
	*
	* Return: true if @vfsgid and @kgid have the same value, false if not.
	* Comparison between two invalid gids returns false.
	*/
	static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t kgid)
	{
	return vfsgid_valid(vfsgid) && __vfsgid_val(vfsgid) == __kgid_val(kgid);
	}

	/*
	* vfs{g,u}ids are created from k{g,u}ids.
	* We don't allow them to be created from regular {u,g}id.
	*/
	#define VFSUIDT_INIT(val) (vfsuid_t){ __kuid_val(val) }
	#define VFSGIDT_INIT(val) (vfsgid_t){ __kgid_val(val) }

	#define INVALID_VFSUID VFSUIDT_INIT(INVALID_UID)
	#define INVALID_VFSGID VFSGIDT_INIT(INVALID_GID)

	/*
	* Allow a vfs{g,u}id to be used as a k{g,u}id where we want to compare
	* whether the mapped value is identical to value of a k{g,u}id.
	*/
	#define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) }
	#define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) }

	#ifdef CONFIG_MULTIUSER
	/**
	* vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups
	* @vfsgid: the mnt gid to match
	*
	* This function can be used to determine whether @vfsuid matches any of the
	* caller's groups.
	*
	* Return: 1 if vfsuid matches caller's groups, 0 if not.
	*/
	static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
	{
	return in_group_p(AS_KGIDT(vfsgid));
	}
	#else
	static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
	{
	return 1;
	}
	#endif

	/**
	* initial_idmapping - check whether this is the initial mapping
	* @ns: idmapping to check
	*
	* Check whether this is the initial mapping, mapping 0 to 0, 1 to 1,
	* [...], 1000 to 1000 [...].
	*
	* Return: true if this is the initial mapping, false if not.
	*/
	static inline bool initial_idmapping(const struct user_namespace *ns)
	{
	return ns == &init_user_ns;
	}

	/**
	* no_idmapping - check whether we can skip remapping a kuid/gid
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	*
	* This function can be used to check whether a remapping between two
	* idmappings is required.
	* An idmapped mount is a mount that has an idmapping attached to it that
	* is different from the filsystem's idmapping and the initial idmapping.
	* If the initial mapping is used or the idmapping of the mount and the
	* filesystem are identical no remapping is required.
	*
	* Return: true if remapping can be skipped, false if not.
	*/
	static inline bool no_idmapping(const struct user_namespace *mnt_userns,
	const struct user_namespace *fs_userns)
	{
	return initial_idmapping(mnt_userns) \|\| mnt_userns == fs_userns;
	}

	/**
	* make_vfsuid - map a filesystem kuid into a mnt_userns
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	* @kuid : kuid to be mapped
	*
	* Take a @kuid and remap it from @fs_userns into @mnt_userns. Use this
	* function when preparing a @kuid to be reported to userspace.
	*
	* If no_idmapping() determines that this is not an idmapped mount we can
	* simply return @kuid unchanged.
	* If initial_idmapping() tells us that the filesystem is not mounted with an
	* idmapping we know the value of @kuid won't change when calling
	* from_kuid() so we can simply retrieve the value via __kuid_val()
	* directly.
	*
	* Return: @kuid mapped according to @mnt_userns.
	* If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
	* returned.
	*/

	static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	kuid_t kuid)
	{
	uid_t uid;

	if (no_idmapping(mnt_userns, fs_userns))
	return VFSUIDT_INIT(kuid);
	if (initial_idmapping(fs_userns))
	uid = __kuid_val(kuid);
	else
	uid = from_kuid(fs_userns, kuid);
	if (uid == (uid_t)-1)
	return INVALID_VFSUID;
	return VFSUIDT_INIT(make_kuid(mnt_userns, uid));
	}

	static inline kuid_t mapped_kuid_fs(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	kuid_t kuid)
	{
	return AS_KUIDT(make_vfsuid(mnt_userns, fs_userns, kuid));
	}

	/**
	* make_vfsgid - map a filesystem kgid into a mnt_userns
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	* @kgid : kgid to be mapped
	*
	* Take a @kgid and remap it from @fs_userns into @mnt_userns. Use this
	* function when preparing a @kgid to be reported to userspace.
	*
	* If no_idmapping() determines that this is not an idmapped mount we can
	* simply return @kgid unchanged.
	* If initial_idmapping() tells us that the filesystem is not mounted with an
	* idmapping we know the value of @kgid won't change when calling
	* from_kgid() so we can simply retrieve the value via __kgid_val()
	* directly.
	*
	* Return: @kgid mapped according to @mnt_userns.
	* If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
	* returned.
	*/

	static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	kgid_t kgid)
	{
	gid_t gid;

	if (no_idmapping(mnt_userns, fs_userns))
	return VFSGIDT_INIT(kgid);
	if (initial_idmapping(fs_userns))
	gid = __kgid_val(kgid);
	else
	gid = from_kgid(fs_userns, kgid);
	if (gid == (gid_t)-1)
	return INVALID_VFSGID;
	return VFSGIDT_INIT(make_kgid(mnt_userns, gid));
	}

	static inline kgid_t mapped_kgid_fs(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	kgid_t kgid)
	{
	return AS_KGIDT(make_vfsgid(mnt_userns, fs_userns, kgid));
	}

	/**
	* from_vfsuid - map a vfsuid into the filesystem idmapping
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	* @vfsuid : vfsuid to be mapped
	*
	* Map @vfsuid into the filesystem idmapping. This function has to be used in
	* order to e.g. write @vfsuid to inode->i_uid.
	*
	* Return: @vfsuid mapped into the filesystem idmapping
	*/
	static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	vfsuid_t vfsuid)
	{
	uid_t uid;

	if (no_idmapping(mnt_userns, fs_userns))
	return AS_KUIDT(vfsuid);
	uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
	if (uid == (uid_t)-1)
	return INVALID_UID;
	if (initial_idmapping(fs_userns))
	return KUIDT_INIT(uid);
	return make_kuid(fs_userns, uid);
	}

	/**
	* mapped_kuid_user - map a user kuid into a mnt_userns
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	* @kuid : kuid to be mapped
	*
	* Use the idmapping of @mnt_userns to remap a @kuid into @fs_userns. Use this
	* function when preparing a @kuid to be written to disk or inode.
	*
	* If no_idmapping() determines that this is not an idmapped mount we can
	* simply return @kuid unchanged.
	* If initial_idmapping() tells us that the filesystem is not mounted with an
	* idmapping we know the value of @kuid won't change when calling
	* make_kuid() so we can simply retrieve the value via KUIDT_INIT()
	* directly.
	*
	* Return: @kuid mapped according to @mnt_userns.
	* If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
	* returned.
	*/
	static inline kuid_t mapped_kuid_user(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	kuid_t kuid)
	{
	return from_vfsuid(mnt_userns, fs_userns, VFSUIDT_INIT(kuid));
	}

	/**
	* vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	* @vfsuid: vfsuid to be mapped
	*
	* Check whether @vfsuid has a mapping in the filesystem idmapping. Use this
	* function to check whether the filesystem idmapping has a mapping for
	* @vfsuid.
	*
	* Return: true if @vfsuid has a mapping in the filesystem, false if not.
	*/
	static inline bool vfsuid_has_fsmapping(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	vfsuid_t vfsuid)
	{
	return uid_valid(from_vfsuid(mnt_userns, fs_userns, vfsuid));
	}

	/**
	* vfsuid_into_kuid - convert vfsuid into kuid
	* @vfsuid: the vfsuid to convert
	*
	* This can be used when a vfsuid is committed as a kuid.
	*
	* Return: a kuid with the value of @vfsuid
	*/
	static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
	{
	return AS_KUIDT(vfsuid);
	}

	/**
	* from_vfsgid - map a vfsgid into the filesystem idmapping
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	* @vfsgid : vfsgid to be mapped
	*
	* Map @vfsgid into the filesystem idmapping. This function has to be used in
	* order to e.g. write @vfsgid to inode->i_gid.
	*
	* Return: @vfsgid mapped into the filesystem idmapping
	*/
	static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	vfsgid_t vfsgid)
	{
	gid_t gid;

	if (no_idmapping(mnt_userns, fs_userns))
	return AS_KGIDT(vfsgid);
	gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
	if (gid == (gid_t)-1)
	return INVALID_GID;
	if (initial_idmapping(fs_userns))
	return KGIDT_INIT(gid);
	return make_kgid(fs_userns, gid);
	}

	/**
	* mapped_kgid_user - map a user kgid into a mnt_userns
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	* @kgid : kgid to be mapped
	*
	* Use the idmapping of @mnt_userns to remap a @kgid into @fs_userns. Use this
	* function when preparing a @kgid to be written to disk or inode.
	*
	* If no_idmapping() determines that this is not an idmapped mount we can
	* simply return @kgid unchanged.
	* If initial_idmapping() tells us that the filesystem is not mounted with an
	* idmapping we know the value of @kgid won't change when calling
	* make_kgid() so we can simply retrieve the value via KGIDT_INIT()
	* directly.
	*
	* Return: @kgid mapped according to @mnt_userns.
	* If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
	* returned.
	*/
	static inline kgid_t mapped_kgid_user(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	kgid_t kgid)
	{
	return from_vfsgid(mnt_userns, fs_userns, VFSGIDT_INIT(kgid));
	}

	/**
	* vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	* @vfsgid: vfsgid to be mapped
	*
	* Check whether @vfsgid has a mapping in the filesystem idmapping. Use this
	* function to check whether the filesystem idmapping has a mapping for
	* @vfsgid.
	*
	* Return: true if @vfsgid has a mapping in the filesystem, false if not.
	*/
	static inline bool vfsgid_has_fsmapping(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	vfsgid_t vfsgid)
	{
	return gid_valid(from_vfsgid(mnt_userns, fs_userns, vfsgid));
	}

	/**
	* vfsgid_into_kgid - convert vfsgid into kgid
	* @vfsgid: the vfsgid to convert
	*
	* This can be used when a vfsgid is committed as a kgid.
	*
	* Return: a kgid with the value of @vfsgid
	*/
	static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
	{
	return AS_KGIDT(vfsgid);
	}

	/**
	* mapped_fsuid - return caller's fsuid mapped up into a mnt_userns
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	*
	* Use this helper to initialize a new vfs or filesystem object based on
	* the caller's fsuid. A common example is initializing the i_uid field of
	* a newly allocated inode triggered by a creation event such as mkdir or
	* O_CREAT. Other examples include the allocation of quotas for a specific
	* user.
	*
	* Return: the caller's current fsuid mapped up according to @mnt_userns.
	*/
	static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns)
	{
	return from_vfsuid(mnt_userns, fs_userns,
	VFSUIDT_INIT(current_fsuid()));
	}

	/**
	* mapped_fsgid - return caller's fsgid mapped up into a mnt_userns
	* @mnt_userns: the mount's idmapping
	* @fs_userns: the filesystem's idmapping
	*
	* Use this helper to initialize a new vfs or filesystem object based on
	* the caller's fsgid. A common example is initializing the i_gid field of
	* a newly allocated inode triggered by a creation event such as mkdir or
	* O_CREAT. Other examples include the allocation of quotas for a specific
	* user.
	*
	* Return: the caller's current fsgid mapped up according to @mnt_userns.
	*/
	static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns)
	{
	return from_vfsgid(mnt_userns, fs_userns,
	VFSGIDT_INIT(current_fsgid()));
	}

	#endif /* _LINUX_MNT_IDMAPPING_H */