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![Nick Piggin](/assets/img/avatar_default.png)
This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. This could easily be extended to put acls under RCU and check them under seqlock, if need be. But this implementation is enough to show the rcu-walk aware permissions code for path lookups is working, and will handle cases where there are no ACLs or ACLs in just the final element. This patch implicity converts tmpfs to rcu-aware permission check. Subsequent patches onvert ext*, xfs, and, btrfs. Each of these uses acl/permission code in a different way, so convert them all to provide templates and proof of concept. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
225 lines
4.7 KiB
C
225 lines
4.7 KiB
C
/*
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* (C) 2005 Andreas Gruenbacher <agruen@suse.de>
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*
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* This file is released under the GPL.
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*
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* Generic ACL support for in-memory filesystems.
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*/
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#include <linux/sched.h>
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#include <linux/gfp.h>
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#include <linux/fs.h>
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#include <linux/generic_acl.h>
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#include <linux/posix_acl.h>
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#include <linux/posix_acl_xattr.h>
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static size_t
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generic_acl_list(struct dentry *dentry, char *list, size_t list_size,
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const char *name, size_t name_len, int type)
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{
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struct posix_acl *acl;
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const char *xname;
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size_t size;
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acl = get_cached_acl(dentry->d_inode, type);
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if (!acl)
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return 0;
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posix_acl_release(acl);
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switch (type) {
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case ACL_TYPE_ACCESS:
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xname = POSIX_ACL_XATTR_ACCESS;
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break;
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case ACL_TYPE_DEFAULT:
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xname = POSIX_ACL_XATTR_DEFAULT;
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break;
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default:
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return 0;
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}
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size = strlen(xname) + 1;
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if (list && size <= list_size)
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memcpy(list, xname, size);
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return size;
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}
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static int
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generic_acl_get(struct dentry *dentry, const char *name, void *buffer,
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size_t size, int type)
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{
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struct posix_acl *acl;
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int error;
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if (strcmp(name, "") != 0)
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return -EINVAL;
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acl = get_cached_acl(dentry->d_inode, type);
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if (!acl)
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return -ENODATA;
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error = posix_acl_to_xattr(acl, buffer, size);
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posix_acl_release(acl);
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return error;
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}
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static int
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generic_acl_set(struct dentry *dentry, const char *name, const void *value,
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size_t size, int flags, int type)
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{
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struct inode *inode = dentry->d_inode;
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struct posix_acl *acl = NULL;
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int error;
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if (strcmp(name, "") != 0)
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return -EINVAL;
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if (S_ISLNK(inode->i_mode))
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return -EOPNOTSUPP;
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if (!is_owner_or_cap(inode))
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return -EPERM;
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if (value) {
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acl = posix_acl_from_xattr(value, size);
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if (IS_ERR(acl))
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return PTR_ERR(acl);
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}
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if (acl) {
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mode_t mode;
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error = posix_acl_valid(acl);
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if (error)
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goto failed;
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switch (type) {
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case ACL_TYPE_ACCESS:
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mode = inode->i_mode;
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error = posix_acl_equiv_mode(acl, &mode);
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if (error < 0)
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goto failed;
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inode->i_mode = mode;
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inode->i_ctime = CURRENT_TIME;
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if (error == 0) {
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posix_acl_release(acl);
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acl = NULL;
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}
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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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error = -EINVAL;
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goto failed;
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}
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break;
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}
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}
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set_cached_acl(inode, type, acl);
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error = 0;
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failed:
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posix_acl_release(acl);
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return error;
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}
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/**
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* generic_acl_init - Take care of acl inheritance at @inode create time
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*
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* Files created inside a directory with a default ACL inherit the
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* directory's default ACL.
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*/
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int
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generic_acl_init(struct inode *inode, struct inode *dir)
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{
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struct posix_acl *acl = NULL;
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mode_t mode = inode->i_mode;
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int error;
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inode->i_mode = mode & ~current_umask();
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if (!S_ISLNK(inode->i_mode))
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acl = get_cached_acl(dir, ACL_TYPE_DEFAULT);
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if (acl) {
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struct posix_acl *clone;
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if (S_ISDIR(inode->i_mode)) {
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clone = posix_acl_clone(acl, GFP_KERNEL);
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error = -ENOMEM;
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if (!clone)
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goto cleanup;
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set_cached_acl(inode, ACL_TYPE_DEFAULT, clone);
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posix_acl_release(clone);
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}
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clone = posix_acl_clone(acl, GFP_KERNEL);
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error = -ENOMEM;
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if (!clone)
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goto cleanup;
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error = posix_acl_create_masq(clone, &mode);
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if (error >= 0) {
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inode->i_mode = mode;
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if (error > 0)
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set_cached_acl(inode, ACL_TYPE_ACCESS, clone);
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}
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posix_acl_release(clone);
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}
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error = 0;
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cleanup:
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posix_acl_release(acl);
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return error;
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}
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/**
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* generic_acl_chmod - change the access acl of @inode upon chmod()
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*
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* A chmod also changes the permissions of the owner, group/mask, and
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* other ACL entries.
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*/
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int
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generic_acl_chmod(struct inode *inode)
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{
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struct posix_acl *acl, *clone;
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int error = 0;
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if (S_ISLNK(inode->i_mode))
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return -EOPNOTSUPP;
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acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
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if (acl) {
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clone = posix_acl_clone(acl, GFP_KERNEL);
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posix_acl_release(acl);
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if (!clone)
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return -ENOMEM;
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error = posix_acl_chmod_masq(clone, inode->i_mode);
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if (!error)
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set_cached_acl(inode, ACL_TYPE_ACCESS, clone);
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posix_acl_release(clone);
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}
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return error;
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}
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int
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generic_check_acl(struct inode *inode, int mask, unsigned int flags)
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{
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if (flags & IPERM_FLAG_RCU) {
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if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
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return -ECHILD;
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} else {
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struct posix_acl *acl;
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acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
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if (acl) {
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int error = posix_acl_permission(inode, acl, mask);
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posix_acl_release(acl);
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return error;
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}
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}
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return -EAGAIN;
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}
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const struct xattr_handler generic_acl_access_handler = {
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.prefix = POSIX_ACL_XATTR_ACCESS,
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.flags = ACL_TYPE_ACCESS,
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.list = generic_acl_list,
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.get = generic_acl_get,
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.set = generic_acl_set,
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};
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const struct xattr_handler generic_acl_default_handler = {
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.prefix = POSIX_ACL_XATTR_DEFAULT,
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.flags = ACL_TYPE_DEFAULT,
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.list = generic_acl_list,
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.get = generic_acl_get,
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.set = generic_acl_set,
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};
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