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;

 /**
  * 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;
 }

 /**
  * mapped_kuid_fs - 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 kuid_t mapped_kuid_fs(struct user_namespace *mnt_userns,
 				    struct user_namespace *fs_userns,
 				    kuid_t kuid)
 {
 	uid_t uid;

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

 /**
  * mapped_kgid_fs - 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 kgid_t mapped_kgid_fs(struct user_namespace *mnt_userns,
 				    struct user_namespace *fs_userns,
 				    kgid_t kgid)
 {
 	gid_t gid;

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

 /**
  * 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)
 {
 	uid_t uid;

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

 /**
  * 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)
 {
 	gid_t gid;

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

 /**
  * 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 mapped_kuid_user(mnt_userns, fs_userns, 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 mapped_kgid_user(mnt_userns, fs_userns, 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;

	/**
	* 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;
	}

	/**
	* mapped_kuid_fs - 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 kuid_t mapped_kuid_fs(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	kuid_t kuid)
	{
	uid_t uid;

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

	/**
	* mapped_kgid_fs - 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 kgid_t mapped_kgid_fs(struct user_namespace *mnt_userns,
	struct user_namespace *fs_userns,
	kgid_t kgid)
	{
	gid_t gid;

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

	/**
	* 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)
	{
	uid_t uid;

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

	/**
	* 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)
	{
	gid_t gid;

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

	/**
	* 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 mapped_kuid_user(mnt_userns, fs_userns, 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 mapped_kgid_user(mnt_userns, fs_userns, current_fsgid());
	}

	#endif /* _LINUX_MNT_IDMAPPING_H */