Fixed MTP to work with TWRP

fs/afs/security.c

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