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![Seth Forshee](/assets/img/avatar_default.png)
INVALID_VFS{U,G}ID represent ids which have no mapping in the target mnt_usersns. This can happen for a couple of different reasons -- the source id might be valid but has no mapping in mnt_userns, or the source id might have been invalid (either due to a failed mapping or because it was set to invalid to indicate it is uninitialized). This means that two arbitrary vfs{u,g}ids which are both invalid could represent two different underlying ids, or they could represent a failed mapping and an uninitialized value. In these situation the vfs{u,g}id equality functions evaluate these ids as equal, and care must be taken when comparing ids to avoid problems. It would be less error prone to always evaluate two invalid ids as not equal to each other, and to check explicitly for vfs{u,g}id validity when that is needed. Change all vfs{u,g}id equality functions to return false when both ids are invalid. Functions for checking whether an id is valid exist and are already being used by code which needs to check this. Link: https://lore.kernel.org/linux-fsdevel/YrIMZirGoE0VIO45@do-x1extreme Signed-off-by: Seth Forshee <sforshee@digitalocean.com> Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
447 lines
14 KiB
C
447 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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* @kuid: the kuid to compare
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* @vfsuid: the vfsuid to compare
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*
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* Check whether @kuid and @vfsuid have the same values.
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*
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* Return: true if @kuid and @vfsuid 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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* @kgid: the kgid to compare
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* @vfsgid: the vfsgid to compare
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*
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* Check whether @kgid and @vfsgid have the same values.
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*
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* Return: true if @kgid and @vfsgid 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(kgid_t kgid, vfsgid_t vfsgid)
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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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* mapped_kuid_fs - 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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* mapped_kgid_fs - 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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* 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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* 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 mapped_kuid_user(mnt_userns, fs_userns, 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 mapped_kgid_user(mnt_userns, fs_userns, current_fsgid());
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}
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#endif /* _LINUX_MNT_IDMAPPING_H */
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