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138060ba92
The current way of setting and getting posix acls through the generic xattr interface is error prone and type unsafe. The vfs needs to interpret and fixup posix acls before storing or reporting it to userspace. Various hacks exist to make this work. The code is hard to understand and difficult to maintain in it's current form. Instead of making this work by hacking posix acls through xattr handlers we are building a dedicated posix acl api around the get and set inode operations. This removes a lot of hackiness and makes the codepaths easier to maintain. A lot of background can be found in [1]. Since some filesystem rely on the dentry being available to them when setting posix acls (e.g., 9p and cifs) they cannot rely on set acl inode operation. But since ->set_acl() is required in order to use the generic posix acl xattr handlers filesystems that do not implement this inode operation cannot use the handler and need to implement their own dedicated posix acl handlers. Update the ->set_acl() inode method to take a dentry argument. This allows all filesystems to rely on ->set_acl(). As far as I can tell all codepaths can be switched to rely on the dentry instead of just the inode. Note that the original motivation for passing the dentry separate from the inode instead of just the dentry in the xattr handlers was because of security modules that call security_d_instantiate(). This hook is called during d_instantiate_new(), d_add(), __d_instantiate_anon(), and d_splice_alias() to initialize the inode's security context and possibly to set security.* xattrs. Since this only affects security.* xattrs this is completely irrelevant for posix acls. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
155 lines
3.3 KiB
C
155 lines
3.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
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* Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
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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/spinlock.h>
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#include <linux/completion.h>
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#include <linux/buffer_head.h>
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#include <linux/xattr.h>
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#include <linux/posix_acl.h>
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#include <linux/posix_acl_xattr.h>
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#include <linux/gfs2_ondisk.h>
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#include "gfs2.h"
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#include "incore.h"
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#include "acl.h"
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#include "xattr.h"
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#include "glock.h"
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#include "inode.h"
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#include "meta_io.h"
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#include "quota.h"
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#include "rgrp.h"
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#include "trans.h"
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#include "util.h"
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static const char *gfs2_acl_name(int type)
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{
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switch (type) {
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case ACL_TYPE_ACCESS:
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return XATTR_POSIX_ACL_ACCESS;
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case ACL_TYPE_DEFAULT:
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return XATTR_POSIX_ACL_DEFAULT;
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}
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return NULL;
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}
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static struct posix_acl *__gfs2_get_acl(struct inode *inode, int type)
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{
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struct gfs2_inode *ip = GFS2_I(inode);
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struct posix_acl *acl;
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const char *name;
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char *data;
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int len;
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if (!ip->i_eattr)
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return NULL;
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name = gfs2_acl_name(type);
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len = gfs2_xattr_acl_get(ip, name, &data);
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if (len <= 0)
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return ERR_PTR(len);
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acl = posix_acl_from_xattr(&init_user_ns, data, len);
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kfree(data);
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return acl;
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}
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struct posix_acl *gfs2_get_acl(struct inode *inode, int type, bool rcu)
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{
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struct gfs2_inode *ip = GFS2_I(inode);
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struct gfs2_holder gh;
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bool need_unlock = false;
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struct posix_acl *acl;
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if (rcu)
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return ERR_PTR(-ECHILD);
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if (!gfs2_glock_is_locked_by_me(ip->i_gl)) {
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int ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED,
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LM_FLAG_ANY, &gh);
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if (ret)
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return ERR_PTR(ret);
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need_unlock = true;
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}
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acl = __gfs2_get_acl(inode, type);
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if (need_unlock)
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gfs2_glock_dq_uninit(&gh);
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return acl;
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}
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int __gfs2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
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{
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int error;
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size_t len;
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char *data;
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const char *name = gfs2_acl_name(type);
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if (acl) {
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len = posix_acl_xattr_size(acl->a_count);
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data = kmalloc(len, GFP_NOFS);
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if (data == NULL)
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return -ENOMEM;
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error = posix_acl_to_xattr(&init_user_ns, acl, data, len);
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if (error < 0)
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goto out;
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} else {
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data = NULL;
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len = 0;
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}
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error = __gfs2_xattr_set(inode, name, data, len, 0, GFS2_EATYPE_SYS);
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if (error)
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goto out;
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set_cached_acl(inode, type, acl);
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out:
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kfree(data);
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return error;
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}
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int gfs2_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
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struct posix_acl *acl, int type)
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{
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struct inode *inode = d_inode(dentry);
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struct gfs2_inode *ip = GFS2_I(inode);
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struct gfs2_holder gh;
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bool need_unlock = false;
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int ret;
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umode_t mode;
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if (acl && acl->a_count > GFS2_ACL_MAX_ENTRIES(GFS2_SB(inode)))
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return -E2BIG;
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ret = gfs2_qa_get(ip);
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if (ret)
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return ret;
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if (!gfs2_glock_is_locked_by_me(ip->i_gl)) {
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ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
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if (ret)
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goto out;
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need_unlock = true;
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}
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mode = inode->i_mode;
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if (type == ACL_TYPE_ACCESS && acl) {
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ret = posix_acl_update_mode(&init_user_ns, inode, &mode, &acl);
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if (ret)
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goto unlock;
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}
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ret = __gfs2_set_acl(inode, acl, type);
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if (!ret && mode != inode->i_mode) {
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inode->i_ctime = current_time(inode);
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inode->i_mode = mode;
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mark_inode_dirty(inode);
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}
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unlock:
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if (need_unlock)
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gfs2_glock_dq_uninit(&gh);
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out:
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gfs2_qa_put(ip);
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return ret;
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}
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