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![Christian Brauner](/assets/img/avatar_default.png)
Now that we ported all places to use the new low-level mapping helpers
that are able to support filesystems mounted with an idmapping we can
remove the old low-level mapping helpers. With the removal of these old
helpers we also conclude the renaming of the mapping helpers we started
in commit a65e58e791
("fs: document and rename fsid helpers").
Link: https://lore.kernel.org/r/20211123114227.3124056-8-brauner@kernel.org (v1)
Link: https://lore.kernel.org/r/20211130121032.3753852-8-brauner@kernel.org (v2)
Link: https://lore.kernel.org/r/20211203111707.3901969-8-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
230 lines
7.5 KiB
C
230 lines
7.5 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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/**
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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 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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uid_t uid;
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if (no_idmapping(mnt_userns, fs_userns))
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return 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_UID;
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return make_kuid(mnt_userns, uid);
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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 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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gid_t gid;
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if (no_idmapping(mnt_userns, fs_userns))
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return 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_GID;
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return make_kgid(mnt_userns, gid);
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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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uid_t uid;
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if (no_idmapping(mnt_userns, fs_userns))
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return kuid;
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uid = from_kuid(mnt_userns, kuid);
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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_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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gid_t gid;
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if (no_idmapping(mnt_userns, fs_userns))
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return kgid;
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gid = from_kgid(mnt_userns, kgid);
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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_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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*
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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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{
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return mapped_kuid_user(mnt_userns, &init_user_ns, 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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*
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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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{
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return mapped_kgid_user(mnt_userns, &init_user_ns, current_fsgid());
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}
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#endif /* _LINUX_MNT_IDMAPPING_H */
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