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![Tycho Andersen](/assets/img/avatar_default.png)
When interacting with extended attributes the vfs verifies that the caller is privileged over the inode with which the extended attribute is associated. For posix access and posix default extended attributes a uid or gid can be stored on-disk. Let the functions handle posix extended attributes on idmapped mounts. If the inode is accessed through an idmapped mount we need to map it according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts. This has no effect for e.g. security xattrs since they don't store uids or gids and don't perform permission checks on them like posix acls do. Link: https://lore.kernel.org/r/20210121131959.646623-10-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Signed-off-by: Tycho Andersen <tycho@tycho.pizza> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
324 lines
7.2 KiB
C
324 lines
7.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* CacheFiles extended attribute management
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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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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/fsnotify.h>
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#include <linux/quotaops.h>
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#include <linux/xattr.h>
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#include <linux/slab.h>
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#include "internal.h"
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static const char cachefiles_xattr_cache[] =
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XATTR_USER_PREFIX "CacheFiles.cache";
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/*
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* check the type label on an object
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* - done using xattrs
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*/
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int cachefiles_check_object_type(struct cachefiles_object *object)
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{
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struct dentry *dentry = object->dentry;
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char type[3], xtype[3];
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int ret;
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ASSERT(dentry);
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ASSERT(d_backing_inode(dentry));
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if (!object->fscache.cookie)
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strcpy(type, "C3");
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else
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snprintf(type, 3, "%02x", object->fscache.cookie->def->type);
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_enter("%p{%s}", object, type);
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/* attempt to install a type label directly */
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ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache, type,
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2, XATTR_CREATE);
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if (ret == 0) {
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_debug("SET"); /* we succeeded */
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goto error;
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}
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if (ret != -EEXIST) {
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pr_err("Can't set xattr on %pd [%lu] (err %d)\n",
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dentry, d_backing_inode(dentry)->i_ino,
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-ret);
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goto error;
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}
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/* read the current type label */
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ret = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, xtype,
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3);
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if (ret < 0) {
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if (ret == -ERANGE)
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goto bad_type_length;
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pr_err("Can't read xattr on %pd [%lu] (err %d)\n",
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dentry, d_backing_inode(dentry)->i_ino,
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-ret);
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goto error;
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}
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/* check the type is what we're expecting */
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if (ret != 2)
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goto bad_type_length;
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if (xtype[0] != type[0] || xtype[1] != type[1])
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goto bad_type;
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ret = 0;
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error:
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_leave(" = %d", ret);
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return ret;
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bad_type_length:
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pr_err("Cache object %lu type xattr length incorrect\n",
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d_backing_inode(dentry)->i_ino);
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ret = -EIO;
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goto error;
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bad_type:
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xtype[2] = 0;
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pr_err("Cache object %pd [%lu] type %s not %s\n",
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dentry, d_backing_inode(dentry)->i_ino,
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xtype, type);
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ret = -EIO;
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goto error;
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}
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/*
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* set the state xattr on a cache file
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*/
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int cachefiles_set_object_xattr(struct cachefiles_object *object,
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struct cachefiles_xattr *auxdata)
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{
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struct dentry *dentry = object->dentry;
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int ret;
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ASSERT(dentry);
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_enter("%p,#%d", object, auxdata->len);
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/* attempt to install the cache metadata directly */
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_debug("SET #%u", auxdata->len);
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clear_bit(FSCACHE_COOKIE_AUX_UPDATED, &object->fscache.cookie->flags);
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ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
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&auxdata->type, auxdata->len, XATTR_CREATE);
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if (ret < 0 && ret != -ENOMEM)
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cachefiles_io_error_obj(
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object,
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"Failed to set xattr with error %d", ret);
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_leave(" = %d", ret);
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return ret;
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}
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/*
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* update the state xattr on a cache file
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*/
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int cachefiles_update_object_xattr(struct cachefiles_object *object,
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struct cachefiles_xattr *auxdata)
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{
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struct dentry *dentry = object->dentry;
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int ret;
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if (!dentry)
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return -ESTALE;
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_enter("%p,#%d", object, auxdata->len);
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/* attempt to install the cache metadata directly */
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_debug("SET #%u", auxdata->len);
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clear_bit(FSCACHE_COOKIE_AUX_UPDATED, &object->fscache.cookie->flags);
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ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
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&auxdata->type, auxdata->len, XATTR_REPLACE);
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if (ret < 0 && ret != -ENOMEM)
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cachefiles_io_error_obj(
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object,
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"Failed to update xattr with error %d", ret);
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_leave(" = %d", ret);
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return ret;
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}
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/*
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* check the consistency between the backing cache and the FS-Cache cookie
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*/
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int cachefiles_check_auxdata(struct cachefiles_object *object)
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{
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struct cachefiles_xattr *auxbuf;
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enum fscache_checkaux validity;
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struct dentry *dentry = object->dentry;
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ssize_t xlen;
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int ret;
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ASSERT(dentry);
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ASSERT(d_backing_inode(dentry));
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ASSERT(object->fscache.cookie->def->check_aux);
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auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
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if (!auxbuf)
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return -ENOMEM;
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xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
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&auxbuf->type, 512 + 1);
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ret = -ESTALE;
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if (xlen < 1 ||
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auxbuf->type != object->fscache.cookie->def->type)
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goto error;
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xlen--;
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validity = fscache_check_aux(&object->fscache, &auxbuf->data, xlen,
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i_size_read(d_backing_inode(dentry)));
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if (validity != FSCACHE_CHECKAUX_OKAY)
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goto error;
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ret = 0;
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error:
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kfree(auxbuf);
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return ret;
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}
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/*
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* check the state xattr on a cache file
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* - return -ESTALE if the object should be deleted
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*/
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int cachefiles_check_object_xattr(struct cachefiles_object *object,
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struct cachefiles_xattr *auxdata)
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{
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struct cachefiles_xattr *auxbuf;
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struct dentry *dentry = object->dentry;
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int ret;
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_enter("%p,#%d", object, auxdata->len);
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ASSERT(dentry);
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ASSERT(d_backing_inode(dentry));
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auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, cachefiles_gfp);
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if (!auxbuf) {
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_leave(" = -ENOMEM");
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return -ENOMEM;
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}
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/* read the current type label */
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ret = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
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&auxbuf->type, 512 + 1);
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if (ret < 0) {
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if (ret == -ENODATA)
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goto stale; /* no attribute - power went off
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* mid-cull? */
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if (ret == -ERANGE)
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goto bad_type_length;
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cachefiles_io_error_obj(object,
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"Can't read xattr on %lu (err %d)",
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d_backing_inode(dentry)->i_ino, -ret);
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goto error;
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}
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/* check the on-disk object */
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if (ret < 1)
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goto bad_type_length;
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if (auxbuf->type != auxdata->type)
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goto stale;
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auxbuf->len = ret;
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/* consult the netfs */
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if (object->fscache.cookie->def->check_aux) {
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enum fscache_checkaux result;
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unsigned int dlen;
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dlen = auxbuf->len - 1;
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_debug("checkaux %s #%u",
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object->fscache.cookie->def->name, dlen);
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result = fscache_check_aux(&object->fscache,
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&auxbuf->data, dlen,
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i_size_read(d_backing_inode(dentry)));
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switch (result) {
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/* entry okay as is */
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case FSCACHE_CHECKAUX_OKAY:
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goto okay;
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/* entry requires update */
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case FSCACHE_CHECKAUX_NEEDS_UPDATE:
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break;
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/* entry requires deletion */
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case FSCACHE_CHECKAUX_OBSOLETE:
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goto stale;
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default:
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BUG();
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}
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/* update the current label */
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ret = vfs_setxattr(&init_user_ns, dentry,
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cachefiles_xattr_cache, &auxdata->type,
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auxdata->len, XATTR_REPLACE);
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if (ret < 0) {
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cachefiles_io_error_obj(object,
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"Can't update xattr on %lu"
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" (error %d)",
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d_backing_inode(dentry)->i_ino, -ret);
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goto error;
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}
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}
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okay:
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ret = 0;
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error:
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kfree(auxbuf);
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_leave(" = %d", ret);
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return ret;
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bad_type_length:
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pr_err("Cache object %lu xattr length incorrect\n",
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d_backing_inode(dentry)->i_ino);
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ret = -EIO;
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goto error;
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stale:
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ret = -ESTALE;
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goto error;
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}
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/*
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* remove the object's xattr to mark it stale
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*/
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int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
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struct dentry *dentry)
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{
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int ret;
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ret = vfs_removexattr(&init_user_ns, dentry, cachefiles_xattr_cache);
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if (ret < 0) {
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if (ret == -ENOENT || ret == -ENODATA)
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ret = 0;
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else if (ret != -ENOMEM)
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cachefiles_io_error(cache,
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"Can't remove xattr from %lu"
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" (error %d)",
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d_backing_inode(dentry)->i_ino, -ret);
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}
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_leave(" = %d", ret);
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return ret;
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}
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