Re: [PATCH v2 02/10] fs: move mapping helpers

Seth Forshee
2021-12-02T17:10:18Z

On Tue, Nov 30, 2021 at 01:10:24PM +0100, Christian Brauner wrote:
> From: Christian Brauner <christian.brauner@ubuntu.com>
>
> The low-level mapping helpers were so far crammed into fs.h. They are
> out of place there. The fs.h header should just contain the higher-level
> mapping helpers that interact directly with vfs objects such as struct
> super_block or struct inode and not the bare mapping helpers. Similarly,
> only vfs and specific fs code shall interact with low-level mapping
> helpers. And so they won't be made accessible automatically through
> regular {g,u}id helpers.
>
> Link: https://lore.kernel.org/r/20211123114227.3124056-3-brauner@kernel.org (v1)
> Cc: Seth Forshee <sforshee@digitalocean.com>
> Cc: Amir Goldstein <amir73il@gmail.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> CC: linux-fsdevel@vger.kernel.org
> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Reviewed-by: Seth Forshee <sforshee@digitalocean.com>

> ---
> /* v2 */
> - Amir Goldstein <amir73il@gmail.com>:
> - Rename header to mnt_idmapping.h
> - Include mnt_idmapping.h header in all files where it is used to
> avoid unnecessary recompliation on header change.
> ---
> fs/ksmbd/smbacl.c | 1 +
> fs/ksmbd/smbacl.h | 1 +
> fs/open.c | 1 +
> fs/posix_acl.c | 1 +
> fs/xfs/xfs_linux.h | 1 +
> include/linux/fs.h | 91 +-----------------------------
> include/linux/mnt_idmapping.h | 101 ++++++++++++++++++++++++++++++++++
> security/commoncap.c | 1 +
> 8 files changed, 108 insertions(+), 90 deletions(-)
> create mode 100644 include/linux/mnt_idmapping.h
>
> diff --git a/fs/ksmbd/smbacl.c b/fs/ksmbd/smbacl.c
> index bd792db32623..ab8099e0fd7f 100644
> --- a/fs/ksmbd/smbacl.c
> +++ b/fs/ksmbd/smbacl.c
> @@ -9,6 +9,7 @@
> #include <linux/fs.h>
> #include <linux/slab.h>
> #include <linux/string.h>
> +#include <linux/mnt_idmapping.h>
>
> #include "smbacl.h"
> #include "smb_common.h"
> diff --git a/fs/ksmbd/smbacl.h b/fs/ksmbd/smbacl.h
> index 73e08cad412b..eba1ebb9e92e 100644
> --- a/fs/ksmbd/smbacl.h
> +++ b/fs/ksmbd/smbacl.h
> @@ -11,6 +11,7 @@
> #include <linux/fs.h>
> #include <linux/namei.h>
> #include <linux/posix_acl.h>
> +#include <linux/mnt_idmapping.h>
>
> #include "mgmt/tree_connect.h"
>
> diff --git a/fs/open.c b/fs/open.c
> index f732fb94600c..2450cc1a2f64 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -32,6 +32,7 @@
> #include <linux/ima.h>
> #include <linux/dnotify.h>
> #include <linux/compat.h>
> +#include <linux/mnt_idmapping.h>
>
> #include "internal.h"
>
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 9323a854a60a..632bfdcf7cc0 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -23,6 +23,7 @@
> #include <linux/export.h>
> #include <linux/user_namespace.h>
> #include <linux/namei.h>
> +#include <linux/mnt_idmapping.h>
>
> static struct posix_acl **acl_by_type(struct inode *inode, int type)
> {
> diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
> index c174262a074e..09a8fba84ff9 100644
> --- a/fs/xfs/xfs_linux.h
> +++ b/fs/xfs/xfs_linux.h
> @@ -61,6 +61,7 @@ typedef __u32 xfs_nlink_t;
> #include <linux/ratelimit.h>
> #include <linux/rhashtable.h>
> #include <linux/xattr.h>
> +#include <linux/mnt_idmapping.h>
>
> #include <asm/page.h>
> #include <asm/div64.h>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 426cc7bcbeb8..f5d1ae0a783a 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -41,6 +41,7 @@
> #include <linux/stddef.h>
> #include <linux/mount.h>
> #include <linux/cred.h>
> +#include <linux/mnt_idmapping.h>
>
> #include <asm/byteorder.h>
> #include <uapi/linux/fs.h>
> @@ -1624,34 +1625,6 @@ static inline void i_gid_write(struct inode *inode, gid_t gid)
> inode->i_gid = make_kgid(inode->i_sb->s_user_ns, gid);
> }
>
> -/**
> - * kuid_into_mnt - map a kuid down into a mnt_userns
> - * @mnt_userns: user namespace of the relevant mount
> - * @kuid: kuid to be mapped
> - *
> - * Return: @kuid mapped according to @mnt_userns.
> - * If @kuid has no mapping INVALID_UID is returned.
> - */
> -static inline kuid_t kuid_into_mnt(struct user_namespace *mnt_userns,
> - kuid_t kuid)
> -{
> - return make_kuid(mnt_userns, __kuid_val(kuid));
> -}
> -
> -/**
> - * kgid_into_mnt - map a kgid down into a mnt_userns
> - * @mnt_userns: user namespace of the relevant mount
> - * @kgid: kgid to be mapped
> - *
> - * Return: @kgid mapped according to @mnt_userns.
> - * If @kgid has no mapping INVALID_GID is returned.
> - */
> -static inline kgid_t kgid_into_mnt(struct user_namespace *mnt_userns,
> - kgid_t kgid)
> -{
> - return make_kgid(mnt_userns, __kgid_val(kgid));
> -}
> -
> /**
> * i_uid_into_mnt - map an inode's i_uid down into a mnt_userns
> * @mnt_userns: user namespace of the mount the inode was found from
> @@ -1680,68 +1653,6 @@ static inline kgid_t i_gid_into_mnt(struct user_namespace *mnt_userns,
> return kgid_into_mnt(mnt_userns, inode->i_gid);
> }
>
> -/**
> - * kuid_from_mnt - map a kuid up into a mnt_userns
> - * @mnt_userns: user namespace of the relevant mount
> - * @kuid: kuid to be mapped
> - *
> - * Return: @kuid mapped up according to @mnt_userns.
> - * If @kuid has no mapping INVALID_UID is returned.
> - */
> -static inline kuid_t kuid_from_mnt(struct user_namespace *mnt_userns,
> - kuid_t kuid)
> -{
> - return KUIDT_INIT(from_kuid(mnt_userns, kuid));
> -}
> -
> -/**
> - * kgid_from_mnt - map a kgid up into a mnt_userns
> - * @mnt_userns: user namespace of the relevant mount
> - * @kgid: kgid to be mapped
> - *
> - * Return: @kgid mapped up according to @mnt_userns.
> - * If @kgid has no mapping INVALID_GID is returned.
> - */
> -static inline kgid_t kgid_from_mnt(struct user_namespace *mnt_userns,
> - kgid_t kgid)
> -{
> - return KGIDT_INIT(from_kgid(mnt_userns, kgid));
> -}
> -
> -/**
> - * mapped_fsuid - return caller's fsuid mapped up into a mnt_userns
> - * @mnt_userns: user namespace of the relevant mount
> - *
> - * Use this helper to initialize a new vfs or filesystem object based on
> - * the caller's fsuid. A common example is initializing the i_uid field of
> - * a newly allocated inode triggered by a creation event such as mkdir or
> - * O_CREAT. Other examples include the allocation of quotas for a specific
> - * user.
> - *
> - * Return: the caller's current fsuid mapped up according to @mnt_userns.
> - */
> -static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns)
> -{
> - return kuid_from_mnt(mnt_userns, current_fsuid());
> -}
> -
> -/**
> - * mapped_fsgid - return caller's fsgid mapped up into a mnt_userns
> - * @mnt_userns: user namespace of the relevant mount
> - *
> - * Use this helper to initialize a new vfs or filesystem object based on
> - * the caller's fsgid. A common example is initializing the i_gid field of
> - * a newly allocated inode triggered by a creation event such as mkdir or
> - * O_CREAT. Other examples include the allocation of quotas for a specific
> - * user.
> - *
> - * Return: the caller's current fsgid mapped up according to @mnt_userns.
> - */
> -static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns)
> -{
> - return kgid_from_mnt(mnt_userns, current_fsgid());
> -}
> -
> /**
> * inode_fsuid_set - initialize inode's i_uid field with callers fsuid
> * @inode: inode to initialize
> diff --git a/include/linux/mnt_idmapping.h b/include/linux/mnt_idmapping.h
> new file mode 100644
> index 000000000000..7ff8b66b80cb
> --- /dev/null
> +++ b/include/linux/mnt_idmapping.h
> @@ -0,0 +1,101 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _LINUX_MNT_MAPPING_H
> +#define _LINUX_MNT_MAPPING_H
> +
> +#include <linux/types.h>
> +#include <linux/uidgid.h>
> +
> +struct user_namespace;
> +extern struct user_namespace init_user_ns;
> +
> +/**
> + * kuid_into_mnt - map a kuid down into a mnt_userns
> + * @mnt_userns: user namespace of the relevant mount
> + * @kuid: kuid to be mapped
> + *
> + * Return: @kuid mapped according to @mnt_userns.
> + * If @kuid has no mapping INVALID_UID is returned.
> + */
> +static inline kuid_t kuid_into_mnt(struct user_namespace *mnt_userns,
> + kuid_t kuid)
> +{
> + return make_kuid(mnt_userns, __kuid_val(kuid));
> +}
> +
> +/**
> + * kgid_into_mnt - map a kgid down into a mnt_userns
> + * @mnt_userns: user namespace of the relevant mount
> + * @kgid: kgid to be mapped
> + *
> + * Return: @kgid mapped according to @mnt_userns.
> + * If @kgid has no mapping INVALID_GID is returned.
> + */
> +static inline kgid_t kgid_into_mnt(struct user_namespace *mnt_userns,
> + kgid_t kgid)
> +{
> + return make_kgid(mnt_userns, __kgid_val(kgid));
> +}
> +
> +/**
> + * kuid_from_mnt - map a kuid up into a mnt_userns
> + * @mnt_userns: user namespace of the relevant mount
> + * @kuid: kuid to be mapped
> + *
> + * Return: @kuid mapped up according to @mnt_userns.
> + * If @kuid has no mapping INVALID_UID is returned.
> + */
> +static inline kuid_t kuid_from_mnt(struct user_namespace *mnt_userns,
> + kuid_t kuid)
> +{
> + return KUIDT_INIT(from_kuid(mnt_userns, kuid));
> +}
> +
> +/**
> + * kgid_from_mnt - map a kgid up into a mnt_userns
> + * @mnt_userns: user namespace of the relevant mount
> + * @kgid: kgid to be mapped
> + *
> + * Return: @kgid mapped up according to @mnt_userns.
> + * If @kgid has no mapping INVALID_GID is returned.
> + */
> +static inline kgid_t kgid_from_mnt(struct user_namespace *mnt_userns,
> + kgid_t kgid)
> +{
> + return KGIDT_INIT(from_kgid(mnt_userns, kgid));
> +}
> +
> +/**
> + * mapped_fsuid - return caller's fsuid mapped up into a mnt_userns
> + * @mnt_userns: user namespace of the relevant mount
> + *
> + * Use this helper to initialize a new vfs or filesystem object based on
> + * the caller's fsuid. A common example is initializing the i_uid field of
> + * a newly allocated inode triggered by a creation event such as mkdir or
> + * O_CREAT. Other examples include the allocation of quotas for a specific
> + * user.
> + *
> + * Return: the caller's current fsuid mapped up according to @mnt_userns.
> + */
> +static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns)
> +{
> + return kuid_from_mnt(mnt_userns, current_fsuid());
> +}
> +
> +/**
> + * mapped_fsgid - return caller's fsgid mapped up into a mnt_userns
> + * @mnt_userns: user namespace of the relevant mount
> + *
> + * Use this helper to initialize a new vfs or filesystem object based on
> + * the caller's fsgid. A common example is initializing the i_gid field of
> + * a newly allocated inode triggered by a creation event such as mkdir or
> + * O_CREAT. Other examples include the allocation of quotas for a specific
> + * user.
> + *
> + * Return: the caller's current fsgid mapped up according to @mnt_userns.
> + */
> +static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns)
> +{
> + return kgid_from_mnt(mnt_userns, current_fsgid());
> +}
> +
> +#endif /* _LINUX_MNT_MAPPING_H */
> diff --git a/security/commoncap.c b/security/commoncap.c
> index 3f810d37b71b..09479f71ee2e 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -24,6 +24,7 @@
> #include <linux/user_namespace.h>
> #include <linux/binfmts.h>
> #include <linux/personality.h>
> +#include <linux/mnt_idmapping.h>
>
> /*
> * If a non-root user executes a setuid-root binary in
> --
> 2.30.2
>