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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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