[RFC v3 21/45] richacl: xattr mapping functions

From: Andreas Gruenbacher
Date: Fri Apr 24 2015 - 07:15:22 EST

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Map between "system.richacl" xattrs and the in-kernel representation.

Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
fs/Makefile | 2 +-
fs/richacl_xattr.c | 210 ++++++++++++++++++++++++++++++++++++++++++
fs/xattr.c | 34 +++++--
include/linux/richacl_xattr.h | 52 +++++++++++
include/uapi/linux/xattr.h | 2 +
5 files changed, 293 insertions(+), 7 deletions(-)
create mode 100644 fs/richacl_xattr.c
create mode 100644 include/linux/richacl_xattr.h

diff --git a/fs/Makefile b/fs/Makefile
index bb96ad7..6155cc4 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -48,7 +48,7 @@ obj-$(CONFIG_SYSCTL) += drop_caches.o

obj-$(CONFIG_FHANDLE) += fhandle.o
obj-$(CONFIG_FS_RICHACL) += richacl.o
-richacl-y := richacl_base.o richacl_inode.o
+richacl-y := richacl_base.o richacl_inode.o richacl_xattr.o

obj-y += quota/

diff --git a/fs/richacl_xattr.c b/fs/richacl_xattr.c
new file mode 100644
index 0000000..1fb5b36
--- /dev/null
+++ b/fs/richacl_xattr.c
@@ -0,0 +1,210 @@
+/*
+ * Copyright (C) 2006, 2010 Novell, Inc.
+ * Copyright (C) 2015 Red Hat, Inc.
+ * Written by Andreas Gruenbacher <agruen@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/richacl_xattr.h>
+
+MODULE_LICENSE("GPL");
+
+/**
+ * richacl_from_xattr - convert a richacl xattr into the in-memory representation
+ */
+struct richacl *
+richacl_from_xattr(struct user_namespace *user_ns,
+ const void *value, size_t size)
+{
+ const struct richacl_xattr *xattr_acl = value;
+ const struct richace_xattr *xattr_ace = (void *)(xattr_acl + 1);
+ struct richacl *acl;
+ struct richace *ace;
+ int count;
+
+ if (size < sizeof(*xattr_acl) ||
+ xattr_acl->a_version != RICHACL_XATTR_VERSION ||
+ (xattr_acl->a_flags & ~RICHACL_VALID_FLAGS) ||
+ xattr_acl->a_unused != 0)
+ return ERR_PTR(-EINVAL);
+ size -= sizeof(*xattr_acl);
+ if (size % sizeof(*xattr_ace))
+ return ERR_PTR(-EINVAL);
+ count = size / sizeof(*xattr_ace);
+ if (count > RICHACL_XATTR_MAX_COUNT)
+ return ERR_PTR(-EINVAL);
+
+ acl = richacl_alloc(count, GFP_NOFS);
+ if (!acl)
+ return ERR_PTR(-ENOMEM);
+
+ acl->a_flags = xattr_acl->a_flags;
+ acl->a_owner_mask = le32_to_cpu(xattr_acl->a_owner_mask);
+ if (acl->a_owner_mask & ~RICHACE_VALID_MASK)
+ goto fail_einval;
+ acl->a_group_mask = le32_to_cpu(xattr_acl->a_group_mask);
+ if (acl->a_group_mask & ~RICHACE_VALID_MASK)
+ goto fail_einval;
+ acl->a_other_mask = le32_to_cpu(xattr_acl->a_other_mask);
+ if (acl->a_other_mask & ~RICHACE_VALID_MASK)
+ goto fail_einval;
+
+ richacl_for_each_entry(ace, acl) {
+ ace->e_type = le16_to_cpu(xattr_ace->e_type);
+ ace->e_flags = le16_to_cpu(xattr_ace->e_flags);
+ ace->e_mask = le32_to_cpu(xattr_ace->e_mask);
+
+ if (ace->e_flags & ~RICHACE_VALID_FLAGS)
+ goto fail_einval;
+ if (ace->e_flags & RICHACE_SPECIAL_WHO) {
+ ace->e_id.special = le32_to_cpu(xattr_ace->e_id);
+ if (ace->e_id.special > RICHACE_EVERYONE_SPECIAL_ID)
+ goto fail_einval;
+ } else if (ace->e_flags & RICHACE_IDENTIFIER_GROUP) {
+ ace->e_id.gid = make_kgid(user_ns, le32_to_cpu(xattr_ace->e_id));
+ if (!gid_valid(ace->e_id.gid))
+ goto fail_einval;
+ } else {
+ ace->e_id.uid = make_kuid(user_ns, le32_to_cpu(xattr_ace->e_id));
+ if (!uid_valid(ace->e_id.uid))
+ goto fail_einval;
+ }
+ if (ace->e_type > RICHACE_ACCESS_DENIED_ACE_TYPE ||
+ (ace->e_mask & ~RICHACE_VALID_MASK))
+ goto fail_einval;
+
+ xattr_ace++;
+ }
+
+ return acl;
+
+fail_einval:
+ richacl_put(acl);
+ return ERR_PTR(-EINVAL);
+}
+EXPORT_SYMBOL_GPL(richacl_from_xattr);
+
+/**
+ * richacl_xattr_size - compute the size of the xattr representation of @acl
+ */
+size_t
+richacl_xattr_size(const struct richacl *acl)
+{
+ size_t size = sizeof(struct richacl_xattr);
+
+ size += sizeof(struct richace_xattr) * acl->a_count;
+ return size;
+}
+EXPORT_SYMBOL_GPL(richacl_xattr_size);
+
+/**
+ * richacl_to_xattr - convert @acl into its xattr representation
+ * @acl: the richacl to convert
+ * @buffer: buffer for the result
+ * @size: size of @buffer
+ */
+int
+richacl_to_xattr(struct user_namespace *user_ns,
+ const struct richacl *acl, void *buffer, size_t size)
+{
+ struct richacl_xattr *xattr_acl = buffer;
+ struct richace_xattr *xattr_ace;
+ const struct richace *ace;
+ size_t real_size;
+
+ real_size = richacl_xattr_size(acl);
+ if (!buffer)
+ return real_size;
+ if (real_size > size)
+ return -ERANGE;
+
+ xattr_acl->a_version = RICHACL_XATTR_VERSION;
+ xattr_acl->a_flags = acl->a_flags;
+ xattr_acl->a_unused = 0;
+
+ xattr_acl->a_owner_mask = cpu_to_le32(acl->a_owner_mask);
+ xattr_acl->a_group_mask = cpu_to_le32(acl->a_group_mask);
+ xattr_acl->a_other_mask = cpu_to_le32(acl->a_other_mask);
+
+ xattr_ace = (void *)(xattr_acl + 1);
+ richacl_for_each_entry(ace, acl) {
+ xattr_ace->e_type = cpu_to_le16(ace->e_type);
+ xattr_ace->e_flags = cpu_to_le16(ace->e_flags);
+ xattr_ace->e_mask = cpu_to_le32(ace->e_mask);
+ if (ace->e_flags & RICHACE_SPECIAL_WHO)
+ xattr_ace->e_id = cpu_to_le32(ace->e_id.special);
+ else if (ace->e_flags & RICHACE_IDENTIFIER_GROUP)
+ xattr_ace->e_id =
+ cpu_to_le32(from_kgid(user_ns, ace->e_id.gid));
+ else
+ xattr_ace->e_id =
+ cpu_to_le32(from_kuid(user_ns, ace->e_id.uid));
+ xattr_ace++;
+ }
+ return real_size;
+}
+EXPORT_SYMBOL_GPL(richacl_to_xattr);
+
+/*
+ * Fix up the uids and gids in richacl extended attributes in place.
+ */
+static void richacl_fix_xattr_userns(
+ struct user_namespace *to, struct user_namespace *from,
+ void *value, size_t size)
+{
+ struct richacl_xattr *xattr_acl = value;
+ struct richace_xattr *xattr_ace =
+ (struct richace_xattr *)(xattr_acl + 1);
+ unsigned int count;
+
+ if (!value)
+ return;
+ if (size < sizeof(*xattr_acl))
+ return;
+ if (xattr_acl->a_version != cpu_to_le32(RICHACL_XATTR_VERSION))
+ return;
+ size -= sizeof(*xattr_acl);
+ if (size % sizeof(*xattr_ace))
+ return;
+ count = size / sizeof(*xattr_ace);
+ for (; count; count--, xattr_ace++) {
+ if (xattr_ace->e_flags & cpu_to_le16(RICHACE_SPECIAL_WHO))
+ continue;
+ if (xattr_ace->e_flags & cpu_to_le16(RICHACE_IDENTIFIER_GROUP)) {
+ kgid_t gid = make_kgid(from, le32_to_cpu(xattr_ace->e_id));
+ xattr_ace->e_id = cpu_to_le32(from_kgid(to, gid));
+ } else {
+ kuid_t uid = make_kuid(from, le32_to_cpu(xattr_ace->e_id));
+ xattr_ace->e_id = cpu_to_le32(from_kuid(to, uid));
+ }
+ }
+}
+
+void richacl_fix_xattr_from_user(void *value, size_t size)
+{
+ struct user_namespace *user_ns = current_user_ns();
+ if (user_ns == &init_user_ns)
+ return;
+ richacl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
+}
+
+void richacl_fix_xattr_to_user(void *value, size_t size)
+{
+ struct user_namespace *user_ns = current_user_ns();
+ if (user_ns == &init_user_ns)
+ return;
+ richacl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
+}
diff --git a/fs/xattr.c b/fs/xattr.c
index 4ef6985..a09e654 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -21,6 +21,7 @@
#include <linux/audit.h>
#include <linux/vmalloc.h>
#include <linux/posix_acl_xattr.h>
+#include <linux/richacl_xattr.h>

#include <asm/uaccess.h>

@@ -314,6 +315,18 @@ vfs_removexattr(struct dentry *dentry, const char *name)
}
EXPORT_SYMBOL_GPL(vfs_removexattr);

+static void
+fix_xattr_from_user(const char *kname, void *kvalue, size_t size)
+{
+ if (strncmp(kname, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+ return;
+ kname += XATTR_SYSTEM_PREFIX_LEN;
+ if (!strcmp(kname, XATTR_POSIX_ACL_ACCESS) ||
+ !strcmp(kname, XATTR_POSIX_ACL_DEFAULT))
+ posix_acl_fix_xattr_from_user(kvalue, size);
+ else if (!strcmp(kname, XATTR_RICHACL))
+ richacl_fix_xattr_from_user(kvalue, size);
+}

/*
* Extended attribute SET operations
@@ -350,9 +363,7 @@ setxattr(struct dentry *d, const char __user *name, const void __user *value,
error = -EFAULT;
goto out;
}
- if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
- (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
- posix_acl_fix_xattr_from_user(kvalue, size);
+ fix_xattr_from_user(kname, kvalue, size);
}

error = vfs_setxattr(d, kname, kvalue, size, flags);
@@ -419,6 +430,19 @@ SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
return error;
}

+static void
+fix_xattr_to_user(const char *kname, void *kvalue, size_t size)
+{
+ if (strncmp(kname, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+ return;
+ kname += XATTR_SYSTEM_PREFIX_LEN;
+ if (!strcmp(kname, XATTR_POSIX_ACL_ACCESS) ||
+ !strcmp(kname, XATTR_POSIX_ACL_DEFAULT))
+ posix_acl_fix_xattr_to_user(kvalue, size);
+ else if (!strcmp(kname, XATTR_RICHACL))
+ richacl_fix_xattr_to_user(kvalue, size);
+}
+
/*
* Extended attribute GET operations
*/
@@ -451,9 +475,7 @@ getxattr(struct dentry *d, const char __user *name, void __user *value,

error = vfs_getxattr(d, kname, kvalue, size);
if (error > 0) {
- if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
- (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
- posix_acl_fix_xattr_to_user(kvalue, size);
+ fix_xattr_to_user(kname, kvalue, size);
if (size && copy_to_user(value, kvalue, error))
error = -EFAULT;
} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
diff --git a/include/linux/richacl_xattr.h b/include/linux/richacl_xattr.h
new file mode 100644
index 0000000..13cf746
--- /dev/null
+++ b/include/linux/richacl_xattr.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2006, 2010 Novell, Inc.
+ * Copyright (C) 2015 Red Hat, Inc.
+ * Written by Andreas Gruenbacher <agruen@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+#ifndef __RICHACL_XATTR_H
+#define __RICHACL_XATTR_H
+
+#include <linux/richacl.h>
+
+#define RICHACL_XATTR "system.richacl"
+
+struct richace_xattr {
+ __le16 e_type;
+ __le16 e_flags;
+ __le32 e_mask;
+ __le32 e_id;
+};
+
+struct richacl_xattr {
+ unsigned char a_version;
+ unsigned char a_flags;
+ __le16 a_unused;
+ __le32 a_owner_mask;
+ __le32 a_group_mask;
+ __le32 a_other_mask;
+};
+
+#define RICHACL_XATTR_VERSION 0
+#define RICHACL_XATTR_MAX_COUNT \
+ ((XATTR_SIZE_MAX - sizeof(struct richacl_xattr)) / \
+ sizeof(struct richace_xattr))
+
+extern struct richacl *richacl_from_xattr(struct user_namespace *, const void *, size_t);
+extern size_t richacl_xattr_size(const struct richacl *);
+extern int richacl_to_xattr(struct user_namespace *, const struct richacl *, void *, size_t);
+
+extern void richacl_fix_xattr_from_user(void *, size_t);
+extern void richacl_fix_xattr_to_user(void *, size_t);
+
+#endif /* __RICHACL_XATTR_H */
diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
index 1590c49..1996903 100644
--- a/include/uapi/linux/xattr.h
+++ b/include/uapi/linux/xattr.h
@@ -73,5 +73,7 @@
#define XATTR_POSIX_ACL_DEFAULT "posix_acl_default"
#define XATTR_NAME_POSIX_ACL_DEFAULT XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_DEFAULT

+#define XATTR_RICHACL "richacl"
+#define XATTR_NAME_RICHACL XATTR_SYSTEM_PREFIX XATTR_RICHACL

#endif /* _UAPI_LINUX_XATTR_H */
--
2.1.0

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