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>
131 lines
2.7 KiB
C
131 lines
2.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2007 Red Hat. All rights reserved.
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*/
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#include <linux/fs.h>
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#include <linux/string.h>
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#include <linux/xattr.h>
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#include <linux/posix_acl_xattr.h>
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#include <linux/posix_acl.h>
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#include <linux/sched.h>
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#include <linux/sched/mm.h>
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#include <linux/slab.h>
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#include "ctree.h"
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#include "btrfs_inode.h"
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#include "xattr.h"
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struct posix_acl *btrfs_get_acl(struct inode *inode, int type, bool rcu)
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{
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int size;
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const char *name;
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char *value = NULL;
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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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switch (type) {
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case ACL_TYPE_ACCESS:
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name = XATTR_NAME_POSIX_ACL_ACCESS;
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break;
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case ACL_TYPE_DEFAULT:
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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 = btrfs_getxattr(inode, name, NULL, 0);
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if (size > 0) {
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value = kzalloc(size, GFP_KERNEL);
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if (!value)
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return ERR_PTR(-ENOMEM);
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size = btrfs_getxattr(inode, name, value, size);
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}
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if (size > 0)
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acl = posix_acl_from_xattr(&init_user_ns, value, size);
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else if (size == -ENODATA || size == 0)
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acl = NULL;
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else
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acl = ERR_PTR(size);
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kfree(value);
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return acl;
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}
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int __btrfs_set_acl(struct btrfs_trans_handle *trans, struct inode *inode,
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struct posix_acl *acl, int type)
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{
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int ret, size = 0;
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const char *name;
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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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name = XATTR_NAME_POSIX_ACL_ACCESS;
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break;
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case ACL_TYPE_DEFAULT:
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if (!S_ISDIR(inode->i_mode))
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return acl ? -EINVAL : 0;
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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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unsigned int nofs_flag;
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size = posix_acl_xattr_size(acl->a_count);
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/*
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* We're holding a transaction handle, so use a NOFS memory
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* allocation context to avoid deadlock if reclaim happens.
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*/
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nofs_flag = memalloc_nofs_save();
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value = kmalloc(size, GFP_KERNEL);
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memalloc_nofs_restore(nofs_flag);
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if (!value) {
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ret = -ENOMEM;
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goto out;
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}
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ret = posix_acl_to_xattr(&init_user_ns, acl, value, size);
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if (ret < 0)
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goto out;
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}
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if (trans)
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ret = btrfs_setxattr(trans, inode, name, value, size, 0);
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else
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ret = btrfs_setxattr_trans(inode, name, value, size, 0);
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out:
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kfree(value);
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if (!ret)
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set_cached_acl(inode, type, acl);
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return ret;
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}
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int btrfs_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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int ret;
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struct inode *inode = d_inode(dentry);
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umode_t old_mode = inode->i_mode;
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if (type == ACL_TYPE_ACCESS && acl) {
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ret = posix_acl_update_mode(mnt_userns, inode,
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&inode->i_mode, &acl);
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if (ret)
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return ret;
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}
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ret = __btrfs_set_acl(NULL, inode, acl, type);
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if (ret)
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inode->i_mode = old_mode;
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return ret;
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}
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