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cac2f8b8d8
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]. The current inode operation for getting posix acls takes an inode argument but various filesystems (e.g., 9p, cifs, overlayfs) need access to the dentry. In contrast to the ->set_acl() inode operation we cannot simply extend ->get_acl() to take a dentry argument. The ->get_acl() inode operation is called from: acl_permission_check() -> check_acl() -> get_acl() which is part of generic_permission() which in turn is part of inode_permission(). Both generic_permission() and inode_permission() are called in the ->permission() handler of various filesystems (e.g., overlayfs). So simply passing a dentry argument to ->get_acl() would amount to also having to pass a dentry argument to ->permission(). We should avoid this unnecessary change. So instead of extending the existing inode operation rename it from ->get_acl() to ->get_inode_acl() and add a ->get_acl() method later that passes a dentry argument and which filesystems that need access to the dentry can implement instead of ->get_inode_acl(). Filesystems like cifs which allow setting and getting posix acls but not using them for permission checking during lookup can simply not implement ->get_inode_acl(). This is intended to be a non-functional change. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Suggested-by/Inspired-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
133 lines
3.3 KiB
C
133 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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File: linux/posix_acl.h
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(C) 2002 Andreas Gruenbacher, <a.gruenbacher@computer.org>
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*/
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#ifndef __LINUX_POSIX_ACL_H
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#define __LINUX_POSIX_ACL_H
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#include <linux/bug.h>
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#include <linux/slab.h>
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#include <linux/rcupdate.h>
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#include <linux/refcount.h>
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#include <uapi/linux/posix_acl.h>
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struct user_namespace;
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struct posix_acl_entry {
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short e_tag;
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unsigned short e_perm;
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union {
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kuid_t e_uid;
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kgid_t e_gid;
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};
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};
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struct posix_acl {
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refcount_t a_refcount;
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struct rcu_head a_rcu;
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unsigned int a_count;
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struct posix_acl_entry a_entries[];
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};
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#define FOREACH_ACL_ENTRY(pa, acl, pe) \
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for(pa=(acl)->a_entries, pe=pa+(acl)->a_count; pa<pe; pa++)
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/*
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* Duplicate an ACL handle.
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*/
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static inline struct posix_acl *
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posix_acl_dup(struct posix_acl *acl)
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{
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if (acl)
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refcount_inc(&acl->a_refcount);
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return acl;
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}
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/*
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* Free an ACL handle.
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*/
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static inline void
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posix_acl_release(struct posix_acl *acl)
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{
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if (acl && refcount_dec_and_test(&acl->a_refcount))
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kfree_rcu(acl, a_rcu);
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}
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/* posix_acl.c */
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extern void posix_acl_init(struct posix_acl *, int);
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extern struct posix_acl *posix_acl_alloc(int, gfp_t);
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extern struct posix_acl *posix_acl_from_mode(umode_t, gfp_t);
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extern int posix_acl_equiv_mode(const struct posix_acl *, umode_t *);
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extern int __posix_acl_create(struct posix_acl **, gfp_t, umode_t *);
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extern int __posix_acl_chmod(struct posix_acl **, gfp_t, umode_t);
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extern struct posix_acl *get_posix_acl(struct inode *, int);
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int set_posix_acl(struct user_namespace *, struct dentry *, int,
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struct posix_acl *);
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struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type);
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struct posix_acl *posix_acl_clone(const struct posix_acl *acl, gfp_t flags);
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#ifdef CONFIG_FS_POSIX_ACL
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int posix_acl_chmod(struct user_namespace *, struct dentry *, umode_t);
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extern int posix_acl_create(struct inode *, umode_t *, struct posix_acl **,
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struct posix_acl **);
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int posix_acl_update_mode(struct user_namespace *, struct inode *, umode_t *,
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struct posix_acl **);
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int simple_set_acl(struct user_namespace *, struct dentry *,
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struct posix_acl *, int);
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extern int simple_acl_create(struct inode *, struct inode *);
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struct posix_acl *get_cached_acl(struct inode *inode, int type);
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void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl);
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void forget_cached_acl(struct inode *inode, int type);
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void forget_all_cached_acls(struct inode *inode);
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int posix_acl_valid(struct user_namespace *, const struct posix_acl *);
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int posix_acl_permission(struct user_namespace *, struct inode *,
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const struct posix_acl *, int);
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static inline void cache_no_acl(struct inode *inode)
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{
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inode->i_acl = NULL;
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inode->i_default_acl = NULL;
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}
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#else
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static inline int posix_acl_chmod(struct user_namespace *mnt_userns,
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struct dentry *dentry, umode_t mode)
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{
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return 0;
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}
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#define simple_set_acl NULL
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static inline int simple_acl_create(struct inode *dir, struct inode *inode)
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{
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return 0;
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}
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static inline void cache_no_acl(struct inode *inode)
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{
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}
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static inline int posix_acl_create(struct inode *inode, umode_t *mode,
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struct posix_acl **default_acl, struct posix_acl **acl)
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{
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*default_acl = *acl = NULL;
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return 0;
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}
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static inline void forget_all_cached_acls(struct inode *inode)
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{
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}
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#endif /* CONFIG_FS_POSIX_ACL */
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struct posix_acl *get_inode_acl(struct inode *inode, int type);
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#endif /* __LINUX_POSIX_ACL_H */
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