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

Christian Brauner
2021-11-30T12:11:07Z

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>
---
/* 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