476 lines
14 KiB
C
476 lines
14 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_MNT_IDMAPPING_H
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#define _LINUX_MNT_IDMAPPING_H
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#include <linux/types.h>
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#include <linux/uidgid.h>
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struct user_namespace;
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/*
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* Carries the initial idmapping of 0:0:4294967295 which is an identity
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* mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
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* mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
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*/
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extern struct user_namespace init_user_ns;
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typedef struct {
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uid_t val;
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} vfsuid_t;
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typedef struct {
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gid_t val;
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} vfsgid_t;
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static_assert(sizeof(vfsuid_t) == sizeof(kuid_t));
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static_assert(sizeof(vfsgid_t) == sizeof(kgid_t));
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static_assert(offsetof(vfsuid_t, val) == offsetof(kuid_t, val));
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static_assert(offsetof(vfsgid_t, val) == offsetof(kgid_t, val));
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#ifdef CONFIG_MULTIUSER
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static inline uid_t __vfsuid_val(vfsuid_t uid)
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{
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return uid.val;
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}
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static inline gid_t __vfsgid_val(vfsgid_t gid)
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{
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return gid.val;
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}
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#else
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static inline uid_t __vfsuid_val(vfsuid_t uid)
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{
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return 0;
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}
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static inline gid_t __vfsgid_val(vfsgid_t gid)
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{
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return 0;
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}
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#endif
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static inline bool vfsuid_valid(vfsuid_t uid)
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{
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return __vfsuid_val(uid) != (uid_t)-1;
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}
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static inline bool vfsgid_valid(vfsgid_t gid)
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{
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return __vfsgid_val(gid) != (gid_t)-1;
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}
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static inline bool vfsuid_eq(vfsuid_t left, vfsuid_t right)
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{
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return vfsuid_valid(left) && __vfsuid_val(left) == __vfsuid_val(right);
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}
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static inline bool vfsgid_eq(vfsgid_t left, vfsgid_t right)
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{
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return vfsgid_valid(left) && __vfsgid_val(left) == __vfsgid_val(right);
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}
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/**
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* vfsuid_eq_kuid - check whether kuid and vfsuid have the same value
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* @vfsuid: the vfsuid to compare
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* @kuid: the kuid to compare
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*
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* Check whether @vfsuid and @kuid have the same values.
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*
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* Return: true if @vfsuid and @kuid have the same value, false if not.
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* Comparison between two invalid uids returns false.
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*/
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static inline bool vfsuid_eq_kuid(vfsuid_t vfsuid, kuid_t kuid)
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{
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return vfsuid_valid(vfsuid) && __vfsuid_val(vfsuid) == __kuid_val(kuid);
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}
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/**
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* vfsgid_eq_kgid - check whether kgid and vfsgid have the same value
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* @vfsgid: the vfsgid to compare
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* @kgid: the kgid to compare
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*
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* Check whether @vfsgid and @kgid have the same values.
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*
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* Return: true if @vfsgid and @kgid have the same value, false if not.
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* Comparison between two invalid gids returns false.
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*/
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static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t kgid)
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{
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return vfsgid_valid(vfsgid) && __vfsgid_val(vfsgid) == __kgid_val(kgid);
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}
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/*
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* vfs{g,u}ids are created from k{g,u}ids.
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* We don't allow them to be created from regular {u,g}id.
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*/
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#define VFSUIDT_INIT(val) (vfsuid_t){ __kuid_val(val) }
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#define VFSGIDT_INIT(val) (vfsgid_t){ __kgid_val(val) }
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#define INVALID_VFSUID VFSUIDT_INIT(INVALID_UID)
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#define INVALID_VFSGID VFSGIDT_INIT(INVALID_GID)
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/*
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* Allow a vfs{g,u}id to be used as a k{g,u}id where we want to compare
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* whether the mapped value is identical to value of a k{g,u}id.
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*/
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#define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) }
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#define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) }
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#ifdef CONFIG_MULTIUSER
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/**
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* vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups
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* @vfsgid: the mnt gid to match
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*
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* This function can be used to determine whether @vfsuid matches any of the
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* caller's groups.
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*
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* Return: 1 if vfsuid matches caller's groups, 0 if not.
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*/
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static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
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{
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return in_group_p(AS_KGIDT(vfsgid));
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}
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#else
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static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
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{
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return 1;
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}
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#endif
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/**
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* initial_idmapping - check whether this is the initial mapping
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* @ns: idmapping to check
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*
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* Check whether this is the initial mapping, mapping 0 to 0, 1 to 1,
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* [...], 1000 to 1000 [...].
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*
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* Return: true if this is the initial mapping, false if not.
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*/
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static inline bool initial_idmapping(const struct user_namespace *ns)
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{
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return ns == &init_user_ns;
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}
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/**
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* no_idmapping - check whether we can skip remapping a kuid/gid
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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*
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* This function can be used to check whether a remapping between two
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* idmappings is required.
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* An idmapped mount is a mount that has an idmapping attached to it that
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* is different from the filsystem's idmapping and the initial idmapping.
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* If the initial mapping is used or the idmapping of the mount and the
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* filesystem are identical no remapping is required.
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*
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* Return: true if remapping can be skipped, false if not.
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*/
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static inline bool no_idmapping(const struct user_namespace *mnt_userns,
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const struct user_namespace *fs_userns)
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{
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return initial_idmapping(mnt_userns) || mnt_userns == fs_userns;
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}
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/**
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* make_vfsuid - map a filesystem kuid into a mnt_userns
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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* @kuid : kuid to be mapped
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*
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* Take a @kuid and remap it from @fs_userns into @mnt_userns. Use this
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* function when preparing a @kuid to be reported to userspace.
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*
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* If no_idmapping() determines that this is not an idmapped mount we can
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* simply return @kuid unchanged.
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* If initial_idmapping() tells us that the filesystem is not mounted with an
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* idmapping we know the value of @kuid won't change when calling
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* from_kuid() so we can simply retrieve the value via __kuid_val()
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* directly.
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*
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* Return: @kuid mapped according to @mnt_userns.
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* If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
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* returned.
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*/
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static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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kuid_t kuid)
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{
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uid_t uid;
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if (no_idmapping(mnt_userns, fs_userns))
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return VFSUIDT_INIT(kuid);
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if (initial_idmapping(fs_userns))
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uid = __kuid_val(kuid);
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else
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uid = from_kuid(fs_userns, kuid);
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if (uid == (uid_t)-1)
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return INVALID_VFSUID;
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return VFSUIDT_INIT(make_kuid(mnt_userns, uid));
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}
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static inline kuid_t mapped_kuid_fs(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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kuid_t kuid)
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{
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return AS_KUIDT(make_vfsuid(mnt_userns, fs_userns, kuid));
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}
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/**
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* make_vfsgid - map a filesystem kgid into a mnt_userns
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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* @kgid : kgid to be mapped
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*
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* Take a @kgid and remap it from @fs_userns into @mnt_userns. Use this
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* function when preparing a @kgid to be reported to userspace.
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*
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* If no_idmapping() determines that this is not an idmapped mount we can
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* simply return @kgid unchanged.
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* If initial_idmapping() tells us that the filesystem is not mounted with an
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* idmapping we know the value of @kgid won't change when calling
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* from_kgid() so we can simply retrieve the value via __kgid_val()
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* directly.
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*
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* Return: @kgid mapped according to @mnt_userns.
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* If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
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* returned.
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*/
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static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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kgid_t kgid)
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{
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gid_t gid;
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if (no_idmapping(mnt_userns, fs_userns))
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return VFSGIDT_INIT(kgid);
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if (initial_idmapping(fs_userns))
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gid = __kgid_val(kgid);
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else
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gid = from_kgid(fs_userns, kgid);
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if (gid == (gid_t)-1)
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return INVALID_VFSGID;
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return VFSGIDT_INIT(make_kgid(mnt_userns, gid));
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}
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static inline kgid_t mapped_kgid_fs(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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kgid_t kgid)
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{
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return AS_KGIDT(make_vfsgid(mnt_userns, fs_userns, kgid));
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}
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/**
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* from_vfsuid - map a vfsuid into the filesystem idmapping
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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* @vfsuid : vfsuid to be mapped
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*
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* Map @vfsuid into the filesystem idmapping. This function has to be used in
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* order to e.g. write @vfsuid to inode->i_uid.
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*
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* Return: @vfsuid mapped into the filesystem idmapping
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*/
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static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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vfsuid_t vfsuid)
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{
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uid_t uid;
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if (no_idmapping(mnt_userns, fs_userns))
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return AS_KUIDT(vfsuid);
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uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
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if (uid == (uid_t)-1)
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return INVALID_UID;
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if (initial_idmapping(fs_userns))
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return KUIDT_INIT(uid);
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return make_kuid(fs_userns, uid);
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}
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/**
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* mapped_kuid_user - map a user kuid into a mnt_userns
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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* @kuid : kuid to be mapped
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*
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* Use the idmapping of @mnt_userns to remap a @kuid into @fs_userns. Use this
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* function when preparing a @kuid to be written to disk or inode.
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*
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* If no_idmapping() determines that this is not an idmapped mount we can
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* simply return @kuid unchanged.
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* If initial_idmapping() tells us that the filesystem is not mounted with an
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* idmapping we know the value of @kuid won't change when calling
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* make_kuid() so we can simply retrieve the value via KUIDT_INIT()
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* directly.
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*
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* Return: @kuid mapped according to @mnt_userns.
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* If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
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* returned.
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*/
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static inline kuid_t mapped_kuid_user(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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kuid_t kuid)
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{
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return from_vfsuid(mnt_userns, fs_userns, VFSUIDT_INIT(kuid));
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}
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/**
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* vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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* @vfsuid: vfsuid to be mapped
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*
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* Check whether @vfsuid has a mapping in the filesystem idmapping. Use this
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* function to check whether the filesystem idmapping has a mapping for
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* @vfsuid.
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*
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* Return: true if @vfsuid has a mapping in the filesystem, false if not.
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*/
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static inline bool vfsuid_has_fsmapping(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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vfsuid_t vfsuid)
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{
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return uid_valid(from_vfsuid(mnt_userns, fs_userns, vfsuid));
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}
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/**
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* vfsuid_into_kuid - convert vfsuid into kuid
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* @vfsuid: the vfsuid to convert
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*
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* This can be used when a vfsuid is committed as a kuid.
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*
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* Return: a kuid with the value of @vfsuid
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*/
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static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
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{
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return AS_KUIDT(vfsuid);
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}
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/**
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* from_vfsgid - map a vfsgid into the filesystem idmapping
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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* @vfsgid : vfsgid to be mapped
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*
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* Map @vfsgid into the filesystem idmapping. This function has to be used in
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* order to e.g. write @vfsgid to inode->i_gid.
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*
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* Return: @vfsgid mapped into the filesystem idmapping
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*/
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static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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vfsgid_t vfsgid)
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{
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gid_t gid;
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if (no_idmapping(mnt_userns, fs_userns))
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return AS_KGIDT(vfsgid);
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gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
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if (gid == (gid_t)-1)
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return INVALID_GID;
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if (initial_idmapping(fs_userns))
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return KGIDT_INIT(gid);
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return make_kgid(fs_userns, gid);
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}
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/**
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* mapped_kgid_user - map a user kgid into a mnt_userns
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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* @kgid : kgid to be mapped
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*
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* Use the idmapping of @mnt_userns to remap a @kgid into @fs_userns. Use this
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* function when preparing a @kgid to be written to disk or inode.
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*
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* If no_idmapping() determines that this is not an idmapped mount we can
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* simply return @kgid unchanged.
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* If initial_idmapping() tells us that the filesystem is not mounted with an
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* idmapping we know the value of @kgid won't change when calling
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* make_kgid() so we can simply retrieve the value via KGIDT_INIT()
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* directly.
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*
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* Return: @kgid mapped according to @mnt_userns.
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* If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
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* returned.
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*/
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static inline kgid_t mapped_kgid_user(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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kgid_t kgid)
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{
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return from_vfsgid(mnt_userns, fs_userns, VFSGIDT_INIT(kgid));
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}
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/**
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* vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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* @vfsgid: vfsgid to be mapped
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*
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* Check whether @vfsgid has a mapping in the filesystem idmapping. Use this
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* function to check whether the filesystem idmapping has a mapping for
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* @vfsgid.
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*
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* Return: true if @vfsgid has a mapping in the filesystem, false if not.
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*/
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static inline bool vfsgid_has_fsmapping(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns,
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vfsgid_t vfsgid)
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{
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return gid_valid(from_vfsgid(mnt_userns, fs_userns, vfsgid));
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}
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/**
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* vfsgid_into_kgid - convert vfsgid into kgid
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* @vfsgid: the vfsgid to convert
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*
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* This can be used when a vfsgid is committed as a kgid.
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*
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* Return: a kgid with the value of @vfsgid
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*/
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static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
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{
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return AS_KGIDT(vfsgid);
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}
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/**
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* mapped_fsuid - return caller's fsuid mapped up into a mnt_userns
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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*
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* Use this helper to initialize a new vfs or filesystem object based on
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* the caller's fsuid. A common example is initializing the i_uid field of
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* a newly allocated inode triggered by a creation event such as mkdir or
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* O_CREAT. Other examples include the allocation of quotas for a specific
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* user.
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*
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* Return: the caller's current fsuid mapped up according to @mnt_userns.
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*/
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static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns)
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{
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return from_vfsuid(mnt_userns, fs_userns,
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VFSUIDT_INIT(current_fsuid()));
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}
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/**
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* mapped_fsgid - return caller's fsgid mapped up into a mnt_userns
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* @mnt_userns: the mount's idmapping
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* @fs_userns: the filesystem's idmapping
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*
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* Use this helper to initialize a new vfs or filesystem object based on
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* the caller's fsgid. A common example is initializing the i_gid field of
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* a newly allocated inode triggered by a creation event such as mkdir or
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* O_CREAT. Other examples include the allocation of quotas for a specific
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* user.
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*
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* Return: the caller's current fsgid mapped up according to @mnt_userns.
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*/
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static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns,
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struct user_namespace *fs_userns)
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{
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return from_vfsgid(mnt_userns, fs_userns,
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VFSGIDT_INIT(current_fsgid()));
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}
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#endif /* _LINUX_MNT_IDMAPPING_H */
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