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