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SubjectRe: Generic infrastructure for acls
Date
On Friday, 01 September 2006 23:44, Andrew Morton wrote:
> That's a clumsy-looking interface.

I have added a little documentation now. This will hopefully suffice to
clarify why the interface is as clumsy-looking as it is ;)

Thanks,
Andreas
From: Andreas Gruenbacher <agruen@suse.de>
Subject: Generic infrastructure for acls

Add some infrastructure for access control lists on in-memory
filesystems such as tmpfs.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>

---
fs/Kconfig | 4 +
fs/Makefile | 1
fs/generic_acl.c | 172 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/generic_acl.h | 30 +++++++
4 files changed, 207 insertions(+)

Index: linux-2.6.18-rc6/fs/Kconfig
===================================================================
--- linux-2.6.18-rc6.orig/fs/Kconfig
+++ linux-2.6.18-rc6/fs/Kconfig
@@ -1921,6 +1921,10 @@ config 9P_FS

If unsure, say N.

+config GENERIC_ACL
+ bool
+ select FS_POSIX_ACL
+
endmenu

menu "Partition Types"
Index: linux-2.6.18-rc6/fs/Makefile
===================================================================
--- linux-2.6.18-rc6.orig/fs/Makefile
+++ linux-2.6.18-rc6/fs/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_BINFMT_FLAT) += binfmt_flat
obj-$(CONFIG_FS_MBCACHE) += mbcache.o
obj-$(CONFIG_FS_POSIX_ACL) += posix_acl.o xattr_acl.o
obj-$(CONFIG_NFS_COMMON) += nfs_common/
+obj-$(CONFIG_GENERIC_ACL) += generic_acl.o

obj-$(CONFIG_QUOTA) += dquot.o
obj-$(CONFIG_QFMT_V1) += quota_v1.o
Index: linux-2.6.18-rc6/include/linux/generic_acl.h
===================================================================
--- /dev/null
+++ linux-2.6.18-rc6/include/linux/generic_acl.h
@@ -0,0 +1,36 @@
+/*
+ * fs/generic_acl.c
+ *
+ * (C) 2005 Andreas Gruenbacher <agruen@suse.de>
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef GENERIC_ACL_H
+#define GENERIC_ACL_H
+
+#include <linux/posix_acl.h>
+#include <linux/posix_acl_xattr.h>
+
+/**
+ * struct generic_acl_operations - filesystem operations
+ *
+ * Filesystems must make these operations available to the generic
+ * operations.
+ */
+struct generic_acl_operations {
+ struct posix_acl *(*getacl)(struct inode *, int);
+ void (*setacl)(struct inode *, int, struct posix_acl *);
+};
+
+size_t generic_acl_list(struct inode *, struct generic_acl_operations *, int,
+ char *, size_t);
+int generic_acl_get(struct inode *, struct generic_acl_operations *, int,
+ void *, size_t);
+int generic_acl_set(struct inode *, struct generic_acl_operations *, int,
+ const void *, size_t);
+int generic_acl_init(struct inode *, struct inode *,
+ struct generic_acl_operations *);
+int generic_acl_chmod(struct inode *, struct generic_acl_operations *);
+
+#endif
Index: linux-2.6.18-rc6/fs/generic_acl.c
===================================================================
--- /dev/null
+++ linux-2.6.18-rc6/fs/generic_acl.c
@@ -0,0 +1,197 @@
+/*
+ * fs/generic_acl.c
+ *
+ * (C) 2005 Andreas Gruenbacher <agruen@suse.de>
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/generic_acl.h>
+
+/**
+ * generic_acl_list - Generic xattr_handler->list() operation
+ * @ops: Filesystem specific getacl and setacl callbacks
+ */
+size_t
+generic_acl_list(struct inode *inode, struct generic_acl_operations *ops,
+ int type, char *list, size_t list_size)
+{
+ struct posix_acl *acl;
+ const char *name;
+ size_t size;
+
+ acl = ops->getacl(inode, type);
+ if (!acl)
+ return 0;
+ posix_acl_release(acl);
+
+ switch(type) {
+ case ACL_TYPE_ACCESS:
+ name = POSIX_ACL_XATTR_ACCESS;
+ break;
+
+ case ACL_TYPE_DEFAULT:
+ name = POSIX_ACL_XATTR_DEFAULT;
+ break;
+
+ default:
+ return 0;
+ }
+ size = strlen(name) + 1;
+ if (list && size <= list_size)
+ memcpy(list, name, size);
+ return size;
+}
+
+/**
+ * generic_acl_get - Generic xattr_handler->get() operation
+ * @ops: Filesystem specific getacl and setacl callbacks
+ */
+int
+generic_acl_get(struct inode *inode, struct generic_acl_operations *ops,
+ int type, void *buffer, size_t size)
+{
+ struct posix_acl *acl;
+ int error;
+
+ acl = ops->getacl(inode, type);
+ if (!acl)
+ return -ENODATA;
+ error = posix_acl_to_xattr(acl, buffer, size);
+ posix_acl_release(acl);
+
+ return error;
+}
+
+/**
+ * generic_acl_set - Generic xattr_handler->set() operation
+ * @ops: Filesystem specific getacl and setacl callbacks
+ */
+int
+generic_acl_set(struct inode *inode, struct generic_acl_operations *ops,
+ int type, const void *value, size_t size)
+{
+ struct posix_acl *acl = NULL;
+ int error;
+
+ if (S_ISLNK(inode->i_mode))
+ return -EOPNOTSUPP;
+ if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
+ return -EPERM;
+ if (value) {
+ acl = posix_acl_from_xattr(value, size);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ }
+ if (acl) {
+ mode_t mode;
+
+ error = posix_acl_valid(acl);
+ if (error)
+ goto failed;
+ switch(type) {
+ case ACL_TYPE_ACCESS:
+ mode = inode->i_mode;
+ error = posix_acl_equiv_mode(acl, &mode);
+ if (error < 0)
+ goto failed;
+ inode->i_mode = mode;
+ if (error == 0) {
+ posix_acl_release(acl);
+ acl = NULL;
+ }
+ break;
+
+ case ACL_TYPE_DEFAULT:
+ if (!S_ISDIR(inode->i_mode)) {
+ error = -EINVAL;
+ goto failed;
+ }
+ break;
+ }
+ }
+ ops->setacl(inode, type, acl);
+ error = 0;
+failed:
+ posix_acl_release(acl);
+ return error;
+}
+
+/**
+ * generic_acl_init - Take care of acl inheritance at @inode create time
+ * @ops: Filesystem specific getacl and setacl callbacks
+ *
+ * Files created inside a directory with a default ACL inherit the
+ * directory's default ACL.
+ */
+int
+generic_acl_init(struct inode *inode, struct inode *dir,
+ struct generic_acl_operations *ops)
+{
+ struct posix_acl *acl = NULL;
+ mode_t mode = inode->i_mode;
+ int error;
+
+ inode->i_mode = mode & ~current->fs->umask;
+ if (!S_ISLNK(inode->i_mode))
+ acl = ops->getacl(dir, ACL_TYPE_DEFAULT);
+ if (acl) {
+ struct posix_acl *clone;
+
+ if (S_ISDIR(inode->i_mode)) {
+ clone = posix_acl_clone(acl, GFP_KERNEL);
+ error = -ENOMEM;
+ if (!clone)
+ goto cleanup;
+ ops->setacl(inode, ACL_TYPE_DEFAULT, clone);
+ posix_acl_release(clone);
+ }
+ clone = posix_acl_clone(acl, GFP_KERNEL);
+ error = -ENOMEM;
+ if (!clone)
+ goto cleanup;
+ error = posix_acl_create_masq(clone, &mode);
+ if (error >= 0) {
+ inode->i_mode = mode;
+ if (error > 0)
+ ops->setacl(inode, ACL_TYPE_ACCESS, clone);
+ }
+ posix_acl_release(clone);
+ }
+ error = 0;
+
+cleanup:
+ posix_acl_release(acl);
+ return error;
+}
+
+/**
+ * generic_acl_chmod - change the access acl of @inode upon chmod()
+ * @ops: FIlesystem specific getacl and setacl callbacks
+ *
+ * A chmod also changes the permissions of the owner, group/mask, and
+ * other ACL entries.
+ */
+int
+generic_acl_chmod(struct inode *inode, struct generic_acl_operations *ops)
+{
+ struct posix_acl *acl, *clone;
+ int error = 0;
+
+ if (S_ISLNK(inode->i_mode))
+ return -EOPNOTSUPP;
+ acl = ops->getacl(inode, ACL_TYPE_ACCESS);
+ if (acl) {
+ clone = posix_acl_clone(acl, GFP_KERNEL);
+ posix_acl_release(acl);
+ if (!clone)
+ return -ENOMEM;
+ error = posix_acl_chmod_masq(clone, inode->i_mode);
+ if (!error)
+ ops->setacl(inode, ACL_TYPE_ACCESS, clone);
+ posix_acl_release(clone);
+ }
+ return error;
+}
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