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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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363 lines
8.9 KiB
C
363 lines
8.9 KiB
C
/* AFS security handling
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/ctype.h>
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#include <linux/sched.h>
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#include <keys/rxrpc-type.h>
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#include "internal.h"
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/*
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* get a key
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*/
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struct key *afs_request_key(struct afs_cell *cell)
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{
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struct key *key;
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_enter("{%x}", key_serial(cell->anonymous_key));
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_debug("key %s", cell->anonymous_key->description);
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key = request_key(&key_type_rxrpc, cell->anonymous_key->description,
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NULL);
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if (IS_ERR(key)) {
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if (PTR_ERR(key) != -ENOKEY) {
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_leave(" = %ld", PTR_ERR(key));
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return key;
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}
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/* act as anonymous user */
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_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
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return key_get(cell->anonymous_key);
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} else {
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/* act as authorised user */
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_leave(" = {%x} [auth]", key_serial(key));
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return key;
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}
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}
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/*
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* dispose of a permits list
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*/
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void afs_zap_permits(struct rcu_head *rcu)
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{
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struct afs_permits *permits =
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container_of(rcu, struct afs_permits, rcu);
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int loop;
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_enter("{%d}", permits->count);
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for (loop = permits->count - 1; loop >= 0; loop--)
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key_put(permits->permits[loop].key);
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kfree(permits);
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}
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/*
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* dispose of a permits list in which all the key pointers have been copied
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*/
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static void afs_dispose_of_permits(struct rcu_head *rcu)
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{
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struct afs_permits *permits =
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container_of(rcu, struct afs_permits, rcu);
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_enter("{%d}", permits->count);
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kfree(permits);
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}
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/*
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* get the authorising vnode - this is the specified inode itself if it's a
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* directory or it's the parent directory if the specified inode is a file or
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* symlink
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* - the caller must release the ref on the inode
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*/
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static struct afs_vnode *afs_get_auth_inode(struct afs_vnode *vnode,
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struct key *key)
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{
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struct afs_vnode *auth_vnode;
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struct inode *auth_inode;
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_enter("");
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if (S_ISDIR(vnode->vfs_inode.i_mode)) {
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auth_inode = igrab(&vnode->vfs_inode);
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ASSERT(auth_inode != NULL);
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} else {
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auth_inode = afs_iget(vnode->vfs_inode.i_sb, key,
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&vnode->status.parent, NULL, NULL);
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if (IS_ERR(auth_inode))
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return ERR_CAST(auth_inode);
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}
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auth_vnode = AFS_FS_I(auth_inode);
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_leave(" = {%x}", auth_vnode->fid.vnode);
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return auth_vnode;
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}
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/*
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* clear the permit cache on a directory vnode
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*/
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void afs_clear_permits(struct afs_vnode *vnode)
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{
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struct afs_permits *permits;
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_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
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mutex_lock(&vnode->permits_lock);
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permits = vnode->permits;
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rcu_assign_pointer(vnode->permits, NULL);
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mutex_unlock(&vnode->permits_lock);
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if (permits)
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call_rcu(&permits->rcu, afs_zap_permits);
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_leave("");
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}
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/*
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* add the result obtained for a vnode to its or its parent directory's cache
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* for the key used to access it
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*/
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void afs_cache_permit(struct afs_vnode *vnode, struct key *key, long acl_order)
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{
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struct afs_permits *permits, *xpermits;
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struct afs_permit *permit;
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struct afs_vnode *auth_vnode;
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int count, loop;
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_enter("{%x:%u},%x,%lx",
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vnode->fid.vid, vnode->fid.vnode, key_serial(key), acl_order);
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auth_vnode = afs_get_auth_inode(vnode, key);
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if (IS_ERR(auth_vnode)) {
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_leave(" [get error %ld]", PTR_ERR(auth_vnode));
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return;
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}
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mutex_lock(&auth_vnode->permits_lock);
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/* guard against a rename being detected whilst we waited for the
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* lock */
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if (memcmp(&auth_vnode->fid, &vnode->status.parent,
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sizeof(struct afs_fid)) != 0) {
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_debug("renamed");
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goto out_unlock;
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}
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/* have to be careful as the directory's callback may be broken between
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* us receiving the status we're trying to cache and us getting the
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* lock to update the cache for the status */
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if (auth_vnode->acl_order - acl_order > 0) {
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_debug("ACL changed?");
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goto out_unlock;
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}
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/* always update the anonymous mask */
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_debug("anon access %x", vnode->status.anon_access);
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auth_vnode->status.anon_access = vnode->status.anon_access;
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if (key == vnode->volume->cell->anonymous_key)
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goto out_unlock;
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xpermits = auth_vnode->permits;
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count = 0;
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if (xpermits) {
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/* see if the permit is already in the list
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* - if it is then we just amend the list
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*/
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count = xpermits->count;
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permit = xpermits->permits;
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for (loop = count; loop > 0; loop--) {
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if (permit->key == key) {
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permit->access_mask =
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vnode->status.caller_access;
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goto out_unlock;
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}
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permit++;
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}
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}
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permits = kmalloc(sizeof(*permits) + sizeof(*permit) * (count + 1),
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GFP_NOFS);
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if (!permits)
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goto out_unlock;
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if (xpermits)
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memcpy(permits->permits, xpermits->permits,
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count * sizeof(struct afs_permit));
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_debug("key %x access %x",
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key_serial(key), vnode->status.caller_access);
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permits->permits[count].access_mask = vnode->status.caller_access;
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permits->permits[count].key = key_get(key);
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permits->count = count + 1;
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rcu_assign_pointer(auth_vnode->permits, permits);
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if (xpermits)
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call_rcu(&xpermits->rcu, afs_dispose_of_permits);
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out_unlock:
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mutex_unlock(&auth_vnode->permits_lock);
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iput(&auth_vnode->vfs_inode);
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_leave("");
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}
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/*
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* check with the fileserver to see if the directory or parent directory is
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* permitted to be accessed with this authorisation, and if so, what access it
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* is granted
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*/
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static int afs_check_permit(struct afs_vnode *vnode, struct key *key,
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afs_access_t *_access)
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{
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struct afs_permits *permits;
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struct afs_permit *permit;
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struct afs_vnode *auth_vnode;
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bool valid;
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int loop, ret;
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_enter("{%x:%u},%x",
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vnode->fid.vid, vnode->fid.vnode, key_serial(key));
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auth_vnode = afs_get_auth_inode(vnode, key);
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if (IS_ERR(auth_vnode)) {
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*_access = 0;
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_leave(" = %ld", PTR_ERR(auth_vnode));
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return PTR_ERR(auth_vnode);
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}
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ASSERT(S_ISDIR(auth_vnode->vfs_inode.i_mode));
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/* check the permits to see if we've got one yet */
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if (key == auth_vnode->volume->cell->anonymous_key) {
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_debug("anon");
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*_access = auth_vnode->status.anon_access;
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valid = true;
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} else {
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valid = false;
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rcu_read_lock();
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permits = rcu_dereference(auth_vnode->permits);
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if (permits) {
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permit = permits->permits;
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for (loop = permits->count; loop > 0; loop--) {
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if (permit->key == key) {
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_debug("found in cache");
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*_access = permit->access_mask;
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valid = true;
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break;
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}
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permit++;
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}
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}
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rcu_read_unlock();
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}
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if (!valid) {
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/* check the status on the file we're actually interested in
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* (the post-processing will cache the result on auth_vnode) */
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_debug("no valid permit");
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set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
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ret = afs_vnode_fetch_status(vnode, auth_vnode, key);
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if (ret < 0) {
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iput(&auth_vnode->vfs_inode);
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*_access = 0;
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_leave(" = %d", ret);
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return ret;
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}
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*_access = vnode->status.caller_access;
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}
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iput(&auth_vnode->vfs_inode);
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_leave(" = 0 [access %x]", *_access);
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return 0;
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}
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/*
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* check the permissions on an AFS file
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* - AFS ACLs are attached to directories only, and a file is controlled by its
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* parent directory's ACL
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*/
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int afs_permission(struct inode *inode, int mask)
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{
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struct afs_vnode *vnode = AFS_FS_I(inode);
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afs_access_t uninitialized_var(access);
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struct key *key;
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int ret;
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if (mask & MAY_NOT_BLOCK)
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return -ECHILD;
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_enter("{{%x:%u},%lx},%x,",
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vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
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key = afs_request_key(vnode->volume->cell);
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if (IS_ERR(key)) {
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_leave(" = %ld [key]", PTR_ERR(key));
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return PTR_ERR(key);
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}
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/* if the promise has expired, we need to check the server again */
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if (!vnode->cb_promised) {
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_debug("not promised");
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ret = afs_vnode_fetch_status(vnode, NULL, key);
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if (ret < 0)
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goto error;
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_debug("new promise [fl=%lx]", vnode->flags);
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}
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/* check the permits to see if we've got one yet */
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ret = afs_check_permit(vnode, key, &access);
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if (ret < 0)
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goto error;
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/* interpret the access mask */
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_debug("REQ %x ACC %x on %s",
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mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
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if (S_ISDIR(inode->i_mode)) {
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if (mask & MAY_EXEC) {
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if (!(access & AFS_ACE_LOOKUP))
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goto permission_denied;
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} else if (mask & MAY_READ) {
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if (!(access & AFS_ACE_READ))
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goto permission_denied;
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} else if (mask & MAY_WRITE) {
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if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
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AFS_ACE_INSERT | /* create, mkdir, symlink, rename to */
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AFS_ACE_WRITE))) /* chmod */
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goto permission_denied;
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} else {
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BUG();
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}
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} else {
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if (!(access & AFS_ACE_LOOKUP))
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goto permission_denied;
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if (mask & (MAY_EXEC | MAY_READ)) {
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if (!(access & AFS_ACE_READ))
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goto permission_denied;
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} else if (mask & MAY_WRITE) {
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if (!(access & AFS_ACE_WRITE))
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goto permission_denied;
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}
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}
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key_put(key);
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ret = generic_permission(inode, mask);
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_leave(" = %d", ret);
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return ret;
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permission_denied:
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ret = -EACCES;
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error:
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key_put(key);
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_leave(" = %d", ret);
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return ret;
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}
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