fs/xattr_acl.c

   1 /*
   2  * linux/fs/xattr_acl.c
   3  *
   4  * Almost all from linux/fs/ext2/acl.c:
   5  * Copyright (C) 2001 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
   6  */
   7
   8 #include <linux/export.h>
   9 #include <linux/fs.h>
  10 #include <linux/posix_acl_xattr.h>
  11 #include <linux/gfp.h>
  12 #include <linux/user_namespace.h>
  13
  14 /*
  15  * Fix up the uids and gids in posix acl extended attributes in place.
  16  */
  17 static void posix_acl_fix_xattr_userns(
  18         struct user_namespace *to, struct user_namespace *from,
  19         void *value, size_t size)
  20 {
  21         posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
  22         posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
  23         int count;
  24         kuid_t uid;
  25         kgid_t gid;
  26
  27         if (!value)
  28                 return;
  29         if (size < sizeof(posix_acl_xattr_header))
  30                 return;
  31         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
  32                 return;
  33
  34         count = posix_acl_xattr_count(size);
  35         if (count < 0)
  36                 return;
  37         if (count == 0)
  38                 return;
  39
  40         for (end = entry + count; entry != end; entry++) {
  41                 switch(le16_to_cpu(entry->e_tag)) {
  42                 case ACL_USER:
  43                         uid = make_kuid(from, le32_to_cpu(entry->e_id));
  44                         entry->e_id = cpu_to_le32(from_kuid(to, uid));
  45                         break;
  46                 case ACL_GROUP:
  47                         gid = make_kgid(from, le32_to_cpu(entry->e_id));
  48                         entry->e_id = cpu_to_le32(from_kuid(to, uid));
  49                         break;
  50                 default:
  51                         break;
  52                 }
  53         }
  54 }
  55
  56 void posix_acl_fix_xattr_from_user(void *value, size_t size)
  57 {
  58         struct user_namespace *user_ns = current_user_ns();
  59         if (user_ns == &init_user_ns)
  60                 return;
  61         posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
  62 }
  63
  64 void posix_acl_fix_xattr_to_user(void *value, size_t size)
  65 {
  66         struct user_namespace *user_ns = current_user_ns();
  67         if (user_ns == &init_user_ns)
  68                 return;
  69         posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
  70 }
  71
  72 /*
  73  * Convert from extended attribute to in-memory representation.
  74  */
  75 struct posix_acl *
  76 posix_acl_from_xattr(const void *value, size_t size)
  77 {
  78         posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
  79         posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
  80         int count;
  81         struct posix_acl *acl;
  82         struct posix_acl_entry *acl_e;
  83
  84         if (!value)
  85                 return NULL;
  86         if (size < sizeof(posix_acl_xattr_header))
  87                  return ERR_PTR(-EINVAL);
  88         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
  89                 return ERR_PTR(-EOPNOTSUPP);
  90
  91         count = posix_acl_xattr_count(size);
  92         if (count < 0)
  93                 return ERR_PTR(-EINVAL);
  94         if (count == 0)
  95                 return NULL;
  96
  97         acl = posix_acl_alloc(count, GFP_NOFS);
  98         if (!acl)
  99                 return ERR_PTR(-ENOMEM);
 100         acl_e = acl->a_entries;
 101
 102         for (end = entry + count; entry != end; acl_e++, entry++) {
 103                 acl_e->e_tag  = le16_to_cpu(entry->e_tag);
 104                 acl_e->e_perm = le16_to_cpu(entry->e_perm);
 105
 106                 switch(acl_e->e_tag) {
 107                         case ACL_USER_OBJ:
 108                         case ACL_GROUP_OBJ:
 109                         case ACL_MASK:
 110                         case ACL_OTHER:
 111                                 break;
 112
 113                         case ACL_USER:
 114                                 acl_e->e_uid =
 115                                         make_kuid(&init_user_ns,
 116                                                   le32_to_cpu(entry->e_id));
 117                                 if (!uid_valid(acl_e->e_uid))
 118                                         goto fail;
 119                                 break;
 120                         case ACL_GROUP:
 121                                 acl_e->e_gid =
 122                                         make_kgid(&init_user_ns,
 123                                                   le32_to_cpu(entry->e_id));
 124                                 if (!gid_valid(acl_e->e_gid))
 125                                         goto fail;
 126                                 break;
 127
 128                         default:
 129                                 goto fail;
 130                 }
 131         }
 132         return acl;
 133
 134 fail:
 135         posix_acl_release(acl);
 136         return ERR_PTR(-EINVAL);
 137 }
 138 EXPORT_SYMBOL (posix_acl_from_xattr);
 139
 140 /*
 141  * Convert from in-memory to extended attribute representation.
 142  */
 143 int
 144 posix_acl_to_xattr(const struct posix_acl *acl, void *buffer, size_t size)
 145 {
 146         posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
 147         posix_acl_xattr_entry *ext_entry = ext_acl->a_entries;
 148         int real_size, n;
 149
 150         real_size = posix_acl_xattr_size(acl->a_count);
 151         if (!buffer)
 152                 return real_size;
 153         if (real_size > size)
 154                 return -ERANGE;
 155
 156         ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
 157
 158         for (n=0; n < acl->a_count; n++, ext_entry++) {
 159                 const struct posix_acl_entry *acl_e = &acl->a_entries[n];
 160                 ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
 161                 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
 162                 switch(acl_e->e_tag) {
 163                 case ACL_USER:
 164                         ext_entry->e_id =
 165                                 cpu_to_le32(from_kuid(&init_user_ns, acl_e->e_uid));
 166                         break;
 167                 case ACL_GROUP:
 168                         ext_entry->e_id =
 169                                 cpu_to_le32(from_kgid(&init_user_ns, acl_e->e_gid));
 170                         break;
 171                 default:
 172                         ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
 173                         break;
 174                 }
 175         }
 176         return real_size;
 177 }
 178 EXPORT_SYMBOL (posix_acl_to_xattr);