![Andreas Gruenbacher](/assets/img/avatar_default.png)
When get_acl() is called for an inode whose ACL is not cached yet, the get_acl inode operation is called to fetch the ACL from the filesystem. The inode operation is responsible for updating the cached acl with set_cached_acl(). This is done without locking at the VFS level, so another task can call set_cached_acl() or forget_cached_acl() before the get_acl inode operation gets to calling set_cached_acl(), and then get_acl's call to set_cached_acl() results in caching an outdate ACL. Prevent this from happening by setting the cached ACL pointer to a task-specific sentinel value before calling the get_acl inode operation. Move the responsibility for updating the cached ACL from the get_acl inode operations to get_acl(). There, only set the cached ACL if the sentinel value hasn't changed. The sentinel values are chosen to have odd values. Likewise, the value of ACL_NOT_CACHED is odd. In contrast, ACL object pointers always have an even value (ACLs are aligned in memory). This allows to distinguish uncached ACLs values from ACL objects. In addition, switch from guarding inode->i_acl and inode->i_default_acl upates by the inode->i_lock spinlock to using xchg() and cmpxchg(). Filesystems that do not want ACLs returned from their get_acl inode operations to be cached must call forget_cached_acl() to prevent the VFS from doing so. (Patch written by Al Viro and Andreas Gruenbacher.) Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
156 lines
3.6 KiB
C
156 lines
3.6 KiB
C
/*
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* Copyright (C) International Business Machines Corp., 2002-2004
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* Copyright (C) Andreas Gruenbacher, 2001
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* Copyright (C) Linus Torvalds, 1991, 1992
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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* the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/posix_acl_xattr.h>
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#include "jfs_incore.h"
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#include "jfs_txnmgr.h"
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#include "jfs_xattr.h"
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#include "jfs_acl.h"
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struct posix_acl *jfs_get_acl(struct inode *inode, int type)
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{
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struct posix_acl *acl;
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char *ea_name;
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int size;
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char *value = NULL;
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switch(type) {
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case ACL_TYPE_ACCESS:
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ea_name = XATTR_NAME_POSIX_ACL_ACCESS;
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break;
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case ACL_TYPE_DEFAULT:
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ea_name = XATTR_NAME_POSIX_ACL_DEFAULT;
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break;
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default:
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return ERR_PTR(-EINVAL);
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}
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size = __jfs_getxattr(inode, ea_name, NULL, 0);
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if (size > 0) {
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value = kmalloc(size, GFP_KERNEL);
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if (!value)
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return ERR_PTR(-ENOMEM);
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size = __jfs_getxattr(inode, ea_name, value, size);
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}
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if (size < 0) {
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if (size == -ENODATA)
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acl = NULL;
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else
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acl = ERR_PTR(size);
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} else {
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acl = posix_acl_from_xattr(&init_user_ns, value, size);
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}
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kfree(value);
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return acl;
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}
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static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
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struct posix_acl *acl)
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{
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char *ea_name;
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int rc;
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int size = 0;
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char *value = NULL;
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switch (type) {
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case ACL_TYPE_ACCESS:
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ea_name = XATTR_NAME_POSIX_ACL_ACCESS;
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if (acl) {
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rc = posix_acl_equiv_mode(acl, &inode->i_mode);
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if (rc < 0)
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return rc;
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inode->i_ctime = CURRENT_TIME;
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mark_inode_dirty(inode);
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if (rc == 0)
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acl = NULL;
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}
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break;
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case ACL_TYPE_DEFAULT:
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ea_name = XATTR_NAME_POSIX_ACL_DEFAULT;
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break;
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default:
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return -EINVAL;
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}
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if (acl) {
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size = posix_acl_xattr_size(acl->a_count);
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value = kmalloc(size, GFP_KERNEL);
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if (!value)
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return -ENOMEM;
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rc = posix_acl_to_xattr(&init_user_ns, acl, value, size);
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if (rc < 0)
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goto out;
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}
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rc = __jfs_setxattr(tid, inode, ea_name, value, size, 0);
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out:
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kfree(value);
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if (!rc)
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set_cached_acl(inode, type, acl);
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return rc;
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}
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int jfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
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{
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int rc;
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tid_t tid;
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tid = txBegin(inode->i_sb, 0);
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mutex_lock(&JFS_IP(inode)->commit_mutex);
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rc = __jfs_set_acl(tid, inode, type, acl);
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if (!rc)
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rc = txCommit(tid, 1, &inode, 0);
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txEnd(tid);
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mutex_unlock(&JFS_IP(inode)->commit_mutex);
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return rc;
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}
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int jfs_init_acl(tid_t tid, struct inode *inode, struct inode *dir)
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{
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struct posix_acl *default_acl, *acl;
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int rc = 0;
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rc = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
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if (rc)
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return rc;
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if (default_acl) {
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rc = __jfs_set_acl(tid, inode, ACL_TYPE_DEFAULT, default_acl);
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posix_acl_release(default_acl);
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}
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if (acl) {
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if (!rc)
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rc = __jfs_set_acl(tid, inode, ACL_TYPE_ACCESS, acl);
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posix_acl_release(acl);
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}
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JFS_IP(inode)->mode2 = (JFS_IP(inode)->mode2 & 0xffff0000) |
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inode->i_mode;
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return rc;
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}
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