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/*
* FUSE: Filesystem in Userspace
* Copyright (C) 2016 Canonical Ltd. <seth.forshee@canonical.com>
*
* This program can be distributed under the terms of the GNU GPL.
* See the file COPYING.
*/
#include "fuse_i.h"
#include <linux/posix_acl.h>
#include <linux/posix_acl_xattr.h>
static struct posix_acl *__fuse_get_acl(struct fuse_conn *fc,
struct user_namespace *mnt_userns,
struct inode *inode, int type, bool rcu)
{
int size;
const char *name;
void *value = NULL;
struct posix_acl *acl;
if (rcu)
return ERR_PTR(-ECHILD);
if (fuse_is_bad(inode))
return ERR_PTR(-EIO);
if (fc->no_getxattr)
return NULL;
if (type == ACL_TYPE_ACCESS)
name = XATTR_NAME_POSIX_ACL_ACCESS;
else if (type == ACL_TYPE_DEFAULT)
name = XATTR_NAME_POSIX_ACL_DEFAULT;
else
return ERR_PTR(-EOPNOTSUPP);
value = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!value)
return ERR_PTR(-ENOMEM);
size = fuse_getxattr(inode, name, value, PAGE_SIZE);
if (size > 0)
acl = posix_acl_from_xattr(fc->user_ns, value, size);
else if ((size == 0) || (size == -ENODATA) ||
(size == -EOPNOTSUPP && fc->no_getxattr))
acl = NULL;
else if (size == -ERANGE)
acl = ERR_PTR(-E2BIG);
else
acl = ERR_PTR(size);
kfree(value);
return acl;
}
static inline bool fuse_no_acl(const struct fuse_conn *fc,
const struct inode *inode)
{
/*
* Refuse interacting with POSIX ACLs for daemons that
* don't support FUSE_POSIX_ACL and are not mounted on
* the host to retain backwards compatibility.
*/
return !fc->posix_acl && (i_user_ns(inode) != &init_user_ns);
}
struct posix_acl *fuse_get_acl(struct user_namespace *mnt_userns,
struct dentry *dentry, int type)
{
struct inode *inode = d_inode(dentry);
struct fuse_conn *fc = get_fuse_conn(inode);
if (fuse_no_acl(fc, inode))
return ERR_PTR(-EOPNOTSUPP);
return __fuse_get_acl(fc, mnt_userns, inode, type, false);
}
struct posix_acl *fuse_get_inode_acl(struct inode *inode, int type, bool rcu)
{
struct fuse_conn *fc = get_fuse_conn(inode);
/*
* FUSE daemons before FUSE_POSIX_ACL was introduced could get and set
* POSIX ACLs without them being used for permission checking by the
* vfs. Retain that behavior for backwards compatibility as there are
* filesystems that do all permission checking for acls in the daemon
* and not in the kernel.
*/
if (!fc->posix_acl)
return NULL;
return __fuse_get_acl(fc, &init_user_ns, inode, type, rcu);
}
int fuse_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
struct posix_acl *acl, int type)
{
struct inode *inode = d_inode(dentry);
struct fuse_conn *fc = get_fuse_conn(inode);
const char *name;
int ret;
if (fuse_is_bad(inode))
return -EIO;
if (fc->no_setxattr || fuse_no_acl(fc, inode))
return -EOPNOTSUPP;
if (type == ACL_TYPE_ACCESS)
name = XATTR_NAME_POSIX_ACL_ACCESS;
else if (type == ACL_TYPE_DEFAULT)
name = XATTR_NAME_POSIX_ACL_DEFAULT;
else
return -EINVAL;
if (acl) {
unsigned int extra_flags = 0;
/*
* Fuse userspace is responsible for updating access
* permissions in the inode, if needed. fuse_setxattr
* invalidates the inode attributes, which will force
* them to be refreshed the next time they are used,
* and it also updates i_ctime.
*/
size_t size = posix_acl_xattr_size(acl->a_count);
void *value;
if (size > PAGE_SIZE)
return -E2BIG;
value = kmalloc(size, GFP_KERNEL);
if (!value)
return -ENOMEM;
ret = posix_acl_to_xattr(fc->user_ns, acl, value, size);
if (ret < 0) {
kfree(value);
return ret;
}
/*
* Fuse daemons without FUSE_POSIX_ACL never changed the passed
* through POSIX ACLs. Such daemons don't expect setgid bits to
* be stripped.
*/
if (fc->posix_acl &&
!vfsgid_in_group_p(i_gid_into_vfsgid(&init_user_ns, inode)) &&
!capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID))
extra_flags |= FUSE_SETXATTR_ACL_KILL_SGID;
ret = fuse_setxattr(inode, name, value, size, 0, extra_flags);
kfree(value);
} else {
ret = fuse_removexattr(inode, name);
}
if (fc->posix_acl) {
/*
* Fuse daemons without FUSE_POSIX_ACL never cached POSIX ACLs
* and didn't invalidate attributes. Retain that behavior.
*/
forget_all_cached_acls(inode);
fuse_invalidate_attr(inode);
}
return ret;
}
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