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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>
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_acl(struct inode *inode, int type);
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#endif /* __LINUX_POSIX_ACL_H */
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