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Linux/fs/xattr_acl.c

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  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_kgid(to, gid));
 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(struct user_namespace *user_ns,
 77                      const void *value, size_t size)
 78 {
 79         posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
 80         posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
 81         int count;
 82         struct posix_acl *acl;
 83         struct posix_acl_entry *acl_e;
 84 
 85         if (!value)
 86                 return NULL;
 87         if (size < sizeof(posix_acl_xattr_header))
 88                  return ERR_PTR(-EINVAL);
 89         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 90                 return ERR_PTR(-EOPNOTSUPP);
 91 
 92         count = posix_acl_xattr_count(size);
 93         if (count < 0)
 94                 return ERR_PTR(-EINVAL);
 95         if (count == 0)
 96                 return NULL;
 97         
 98         acl = posix_acl_alloc(count, GFP_NOFS);
 99         if (!acl)
100                 return ERR_PTR(-ENOMEM);
101         acl_e = acl->a_entries;
102         
103         for (end = entry + count; entry != end; acl_e++, entry++) {
104                 acl_e->e_tag  = le16_to_cpu(entry->e_tag);
105                 acl_e->e_perm = le16_to_cpu(entry->e_perm);
106 
107                 switch(acl_e->e_tag) {
108                         case ACL_USER_OBJ:
109                         case ACL_GROUP_OBJ:
110                         case ACL_MASK:
111                         case ACL_OTHER:
112                                 break;
113 
114                         case ACL_USER:
115                                 acl_e->e_uid =
116                                         make_kuid(user_ns,
117                                                   le32_to_cpu(entry->e_id));
118                                 if (!uid_valid(acl_e->e_uid))
119                                         goto fail;
120                                 break;
121                         case ACL_GROUP:
122                                 acl_e->e_gid =
123                                         make_kgid(user_ns,
124                                                   le32_to_cpu(entry->e_id));
125                                 if (!gid_valid(acl_e->e_gid))
126                                         goto fail;
127                                 break;
128 
129                         default:
130                                 goto fail;
131                 }
132         }
133         return acl;
134 
135 fail:
136         posix_acl_release(acl);
137         return ERR_PTR(-EINVAL);
138 }
139 EXPORT_SYMBOL (posix_acl_from_xattr);
140 
141 /*
142  * Convert from in-memory to extended attribute representation.
143  */
144 int
145 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
146                    void *buffer, size_t size)
147 {
148         posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
149         posix_acl_xattr_entry *ext_entry = ext_acl->a_entries;
150         int real_size, n;
151 
152         real_size = posix_acl_xattr_size(acl->a_count);
153         if (!buffer)
154                 return real_size;
155         if (real_size > size)
156                 return -ERANGE;
157         
158         ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
159 
160         for (n=0; n < acl->a_count; n++, ext_entry++) {
161                 const struct posix_acl_entry *acl_e = &acl->a_entries[n];
162                 ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
163                 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
164                 switch(acl_e->e_tag) {
165                 case ACL_USER:
166                         ext_entry->e_id =
167                                 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
168                         break;
169                 case ACL_GROUP:
170                         ext_entry->e_id =
171                                 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
172                         break;
173                 default:
174                         ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
175                         break;
176                 }
177         }
178         return real_size;
179 }
180 EXPORT_SYMBOL (posix_acl_to_xattr);
181 

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