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Subject[PATCH 11/16 v2] pramfs: ACL management
From: Marco Stornelli <marco.stornelli@gmail.com>

ACL operations.

Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
---
diff -Nurp linux-2.6.36-orig/fs/pramfs/acl.c linux-2.6.36/fs/pramfs/acl.c
--- linux-2.6.36-orig/fs/pramfs/acl.c 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.36/fs/pramfs/acl.c 2010-09-14 18:49:52.000000000 +0200
@@ -0,0 +1,418 @@
+/*
+ * FILE NAME fs/pramfs/acl.c
+ *
+ * BRIEF MODULE DESCRIPTION
+ *
+ * POSIX ACL operations
+ *
+ * Copyright 2010 Marco Stornelli <marco.stornelli@gmail.com>
+ *
+ * based on fs/ext2/acl.c with the following copyright:
+ *
+ * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/capability.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include "pram.h"
+#include "xattr.h"
+#include "acl.h"
+
+/*
+ * Load ACL information from filesystem.
+ */
+static struct posix_acl *pram_acl_load(const void *value, size_t size)
+{
+ const char *end = (char *)value + size;
+ int n, count;
+ struct posix_acl *acl;
+
+ if (!value)
+ return NULL;
+ if (size < sizeof(struct pram_acl_header))
+ return ERR_PTR(-EINVAL);
+ if (((struct pram_acl_header *)value)->a_version !=
+ cpu_to_be32(PRAM_ACL_VERSION))
+ return ERR_PTR(-EINVAL);
+ value = (char *)value + sizeof(struct pram_acl_header);
+ count = pram_acl_count(size);
+ if (count < 0)
+ return ERR_PTR(-EINVAL);
+ if (count == 0)
+ return NULL;
+ acl = posix_acl_alloc(count, GFP_KERNEL);
+ if (!acl)
+ return ERR_PTR(-ENOMEM);
+ for (n = 0; n < count; n++) {
+ struct pram_acl_entry *entry = (struct pram_acl_entry *)value;
+ if ((char *)value + sizeof(struct pram_acl_entry_short) > end)
+ goto fail;
+ acl->a_entries[n].e_tag = be16_to_cpu(entry->e_tag);
+ acl->a_entries[n].e_perm = be16_to_cpu(entry->e_perm);
+ switch (acl->a_entries[n].e_tag) {
+ case ACL_USER_OBJ:
+ case ACL_GROUP_OBJ:
+ case ACL_MASK:
+ case ACL_OTHER:
+ value = (char *)value +
+ sizeof(struct pram_acl_entry_short);
+ acl->a_entries[n].e_id = ACL_UNDEFINED_ID;
+ break;
+ case ACL_USER:
+ case ACL_GROUP:
+ value = (char *)value + sizeof(struct pram_acl_entry);
+ if ((char *)value > end)
+ goto fail;
+ acl->a_entries[n].e_id =
+ be32_to_cpu(entry->e_id);
+ break;
+ default:
+ goto fail;
+ }
+ }
+ if (value != end)
+ goto fail;
+ return acl;
+
+fail:
+ posix_acl_release(acl);
+ return ERR_PTR(-EINVAL);
+}
+
+/*
+ * Save ACL information into the filesystem.
+ */
+static void *pram_acl_save(const struct posix_acl *acl, size_t *size)
+{
+ struct pram_acl_header *ext_acl;
+ char *e;
+ size_t n;
+
+ *size = pram_acl_size(acl->a_count);
+ ext_acl = kmalloc(sizeof(struct pram_acl_header) + acl->a_count *
+ sizeof(struct pram_acl_entry), GFP_KERNEL);
+ if (!ext_acl)
+ return ERR_PTR(-ENOMEM);
+ ext_acl->a_version = cpu_to_be32(PRAM_ACL_VERSION);
+ e = (char *)ext_acl + sizeof(struct pram_acl_header);
+ for (n = 0; n < acl->a_count; n++) {
+ struct pram_acl_entry *entry = (struct pram_acl_entry *)e;
+ entry->e_tag = cpu_to_be16(acl->a_entries[n].e_tag);
+ entry->e_perm = cpu_to_be16(acl->a_entries[n].e_perm);
+ switch (acl->a_entries[n].e_tag) {
+ case ACL_USER:
+ case ACL_GROUP:
+ entry->e_id =
+ cpu_to_be32(acl->a_entries[n].e_id);
+ e += sizeof(struct pram_acl_entry);
+ break;
+ case ACL_USER_OBJ:
+ case ACL_GROUP_OBJ:
+ case ACL_MASK:
+ case ACL_OTHER:
+ e += sizeof(struct pram_acl_entry_short);
+ break;
+ default:
+ goto fail;
+ }
+ }
+ return (char *)ext_acl;
+
+fail:
+ kfree(ext_acl);
+ return ERR_PTR(-EINVAL);
+}
+
+/*
+ * inode->i_mutex: don't care
+ */
+static struct posix_acl *pram_get_acl(struct inode *inode, int type)
+{
+ int name_index;
+ char *value = NULL;
+ struct posix_acl *acl;
+ int retval;
+
+ acl = get_cached_acl(inode, type);
+ if (acl != ACL_NOT_CACHED)
+ return acl;
+
+ switch (type) {
+ case ACL_TYPE_ACCESS:
+ name_index = PRAM_XATTR_INDEX_POSIX_ACL_ACCESS;
+ break;
+ case ACL_TYPE_DEFAULT:
+ name_index = PRAM_XATTR_INDEX_POSIX_ACL_DEFAULT;
+ break;
+ default:
+ BUG();
+ }
+ retval = pram_xattr_get(inode, name_index, "", NULL, 0);
+ if (retval > 0) {
+ value = kmalloc(retval, GFP_KERNEL);
+ if (!value)
+ return ERR_PTR(-ENOMEM);
+ retval = pram_xattr_get(inode, name_index, "", value, retval);
+ }
+ if (retval > 0)
+ acl = pram_acl_load(value, retval);
+ else if (retval == -ENODATA || retval == -ENOSYS)
+ acl = NULL;
+ else
+ acl = ERR_PTR(retval);
+ kfree(value);
+
+ if (!IS_ERR(acl))
+ set_cached_acl(inode, type, acl);
+
+ return acl;
+}
+
+/*
+ * inode->i_mutex: down
+ */
+static int pram_set_acl(struct inode *inode, int type, struct posix_acl *acl)
+{
+ int name_index;
+ void *value = NULL;
+ size_t size = 0;
+ int error;
+
+ if (S_ISLNK(inode->i_mode))
+ return -EOPNOTSUPP;
+
+ switch (type) {
+ case ACL_TYPE_ACCESS:
+ name_index = PRAM_XATTR_INDEX_POSIX_ACL_ACCESS;
+ if (acl) {
+ mode_t mode = inode->i_mode;
+ error = posix_acl_equiv_mode(acl, &mode);
+ if (error < 0)
+ return error;
+ else {
+ inode->i_mode = mode;
+ inode->i_ctime = CURRENT_TIME_SEC;
+ mark_inode_dirty(inode);
+ if (error == 0)
+ acl = NULL;
+ }
+ }
+ break;
+ case ACL_TYPE_DEFAULT:
+ name_index = PRAM_XATTR_INDEX_POSIX_ACL_DEFAULT;
+ if (!S_ISDIR(inode->i_mode))
+ return acl ? -EACCES : 0;
+ break;
+ default:
+ return -EINVAL;
+ }
+ if (acl) {
+ value = pram_acl_save(acl, &size);
+ if (IS_ERR(value))
+ return (int)PTR_ERR(value);
+ }
+
+ error = pram_xattr_set(inode, name_index, "", value, size, 0);
+
+ kfree(value);
+ if (!error)
+ set_cached_acl(inode, type, acl);
+ return error;
+}
+
+int pram_check_acl(struct inode *inode, int mask)
+{
+ struct posix_acl *acl = pram_get_acl(inode, ACL_TYPE_ACCESS);
+
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ if (acl) {
+ int error = posix_acl_permission(inode, acl, mask);
+ posix_acl_release(acl);
+ return error;
+ }
+
+ return -EAGAIN;
+}
+
+/*
+ * Initialize the ACLs of a new inode. Called from pram_new_inode.
+ *
+ * dir->i_mutex: down
+ * inode->i_mutex: up (access to inode is still exclusive)
+ */
+int pram_init_acl(struct inode *inode, struct inode *dir)
+{
+ struct posix_acl *acl = NULL;
+ int error = 0;
+
+ if (!S_ISLNK(inode->i_mode)) {
+ acl = pram_get_acl(dir, ACL_TYPE_DEFAULT);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ if (!acl)
+ inode->i_mode &= ~current_umask();
+ }
+
+ if (acl) {
+ struct posix_acl *clone;
+ mode_t mode;
+
+ if (S_ISDIR(inode->i_mode)) {
+ error = pram_set_acl(inode, ACL_TYPE_DEFAULT, acl);
+ if (error)
+ goto cleanup;
+ }
+ clone = posix_acl_clone(acl, GFP_KERNEL);
+ error = -ENOMEM;
+ if (!clone)
+ goto cleanup;
+ mode = inode->i_mode;
+ error = posix_acl_create_masq(clone, &mode);
+ if (error >= 0) {
+ inode->i_mode = mode;
+ if (error > 0) {
+ /* This is an extended ACL */
+ error = pram_set_acl(inode,
+ ACL_TYPE_ACCESS, clone);
+ }
+ }
+ posix_acl_release(clone);
+ }
+cleanup:
+ posix_acl_release(acl);
+ return error;
+}
+
+/*
+ * Does chmod for an inode that may have an Access Control List. The
+ * inode->i_mode field must be updated to the desired value by the caller
+ * before calling this function.
+ * Returns 0 on success, or a negative error number.
+ *
+ * We change the ACL rather than storing some ACL entries in the file
+ * mode permission bits (which would be more efficient), because that
+ * would break once additional permissions (like ACL_APPEND, ACL_DELETE
+ * for directories) are added. There are no more bits available in the
+ * file mode.
+ *
+ * inode->i_mutex: down
+ */
+int pram_acl_chmod(struct inode *inode)
+{
+ struct posix_acl *acl, *clone;
+ int error;
+
+ if (S_ISLNK(inode->i_mode))
+ return -EOPNOTSUPP;
+ acl = pram_get_acl(inode, ACL_TYPE_ACCESS);
+ if (IS_ERR(acl) || !acl)
+ return PTR_ERR(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)
+ error = pram_set_acl(inode, ACL_TYPE_ACCESS, clone);
+ posix_acl_release(clone);
+ return error;
+}
+
+/*
+ * Extended attribut handlers
+ */
+static size_t pram_xattr_list_acl_access(struct dentry *dentry, char *list,
+ size_t list_size, const char *name,
+ size_t name_len, int type)
+{
+ const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
+
+ if (list && size <= list_size)
+ memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
+ return size;
+}
+
+static size_t pram_xattr_list_acl_default(struct dentry *dentry, char *list,
+ size_t list_size, const char *name,
+ size_t name_len, int type)
+{
+ const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
+
+ if (list && size <= list_size)
+ memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
+ return size;
+}
+
+static int pram_xattr_get_acl(struct dentry *dentry, const char *name,
+ void *buffer, size_t size, int type)
+{
+ struct posix_acl *acl;
+ int error;
+
+ if (strcmp(name, "") != 0)
+ return -EINVAL;
+
+ acl = pram_get_acl(dentry->d_inode, type);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ if (acl == NULL)
+ return -ENODATA;
+ error = posix_acl_to_xattr(acl, buffer, size);
+ posix_acl_release(acl);
+
+ return error;
+}
+
+static int pram_xattr_set_acl(struct dentry *dentry, const char *name,
+ const void *value, size_t size, int flags, int type)
+{
+ struct posix_acl *acl;
+ int error;
+
+ if (strcmp(name, "") != 0)
+ return -EINVAL;
+ if (!is_owner_or_cap(dentry->d_inode))
+ return -EPERM;
+
+ if (value) {
+ acl = posix_acl_from_xattr(value, size);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ else if (acl) {
+ error = posix_acl_valid(acl);
+ if (error)
+ goto release_and_out;
+ }
+ } else
+ acl = NULL;
+
+ error = pram_set_acl(dentry->d_inode, type, acl);
+
+release_and_out:
+ posix_acl_release(acl);
+ return error;
+}
+
+const struct xattr_handler pram_xattr_acl_access_handler = {
+ .prefix = POSIX_ACL_XATTR_ACCESS,
+ .flags = ACL_TYPE_ACCESS,
+ .list = pram_xattr_list_acl_access,
+ .get = pram_xattr_get_acl,
+ .set = pram_xattr_set_acl,
+};
+
+const struct xattr_handler pram_xattr_acl_default_handler = {
+ .prefix = POSIX_ACL_XATTR_DEFAULT,
+ .flags = ACL_TYPE_DEFAULT,
+ .list = pram_xattr_list_acl_default,
+ .get = pram_xattr_get_acl,
+ .set = pram_xattr_set_acl,
+};
diff -Nurp linux-2.6.36-orig/fs/pramfs/acl.h linux-2.6.36/fs/pramfs/acl.h
--- linux-2.6.36-orig/fs/pramfs/acl.h 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.36/fs/pramfs/acl.h 2010-09-14 18:49:52.000000000 +0200
@@ -0,0 +1,88 @@
+/*
+ * FILE NAME fs/pramfs/acl.h
+ *
+ * BRIEF MODULE DESCRIPTION
+ *
+ * POSIX ACL operations
+ *
+ * Copyright 2010 Marco Stornelli <marco.stornelli@gmail.com>
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ *
+ * Based on fs/ext2/acl.h with the following copyright:
+ *
+ * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
+ *
+ */
+
+#include <linux/posix_acl_xattr.h>
+
+#define PRAM_ACL_VERSION 0x0001
+
+struct pram_acl_entry {
+ __be16 e_tag;
+ __be16 e_perm;
+ __be32 e_id;
+};
+
+struct pram_acl_entry_short {
+ __be16 e_tag;
+ __be16 e_perm;
+};
+
+struct pram_acl_header {
+ __be32 a_version;
+};
+
+static inline size_t pram_acl_size(int count)
+{
+ if (count <= 4) {
+ return sizeof(struct pram_acl_header) +
+ count * sizeof(struct pram_acl_entry_short);
+ } else {
+ return sizeof(struct pram_acl_header) +
+ 4 * sizeof(struct pram_acl_entry_short) +
+ (count - 4) * sizeof(struct pram_acl_entry);
+ }
+}
+
+static inline int pram_acl_count(size_t size)
+{
+ ssize_t s;
+ size -= sizeof(struct pram_acl_header);
+ s = size - 4 * sizeof(struct pram_acl_entry_short);
+ if (s < 0) {
+ if (size % sizeof(struct pram_acl_entry_short))
+ return -1;
+ return size / sizeof(struct pram_acl_entry_short);
+ } else {
+ if (s % sizeof(struct pram_acl_entry))
+ return -1;
+ return s / sizeof(struct pram_acl_entry) + 4;
+ }
+}
+
+#ifdef CONFIG_PRAMFS_POSIX_ACL
+
+/* acl.c */
+extern int pram_check_acl(struct inode *, int);
+extern int pram_acl_chmod(struct inode *);
+extern int pram_init_acl(struct inode *, struct inode *);
+
+#else
+#include <linux/sched.h>
+#define pram_check_acl NULL
+#define pram_get_acl NULL
+#define pram_set_acl NULL
+
+static inline int pram_acl_chmod(struct inode *inode)
+{
+ return 0;
+}
+
+static inline int pram_init_acl(struct inode *inode, struct inode *dir)
+{
+ return 0;
+}
+#endif


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