fs/nfs_common/nfsacl.c

   1 /*
   2  * fs/nfs_common/nfsacl.c
   3  *
   4  *  Copyright (C) 2002-2003 Andreas Gruenbacher <agruen@suse.de>
   5  */
   6
   7 /*
   8  * The Solaris nfsacl protocol represents some ACLs slightly differently
   9  * than POSIX 1003.1e draft 17 does (and we do):
  10  *
  11  *  - Minimal ACLs always have an ACL_MASK entry, so they have
  12  *    four instead of three entries.
  13  *  - The ACL_MASK entry in such minimal ACLs always has the same
  14  *    permissions as the ACL_GROUP_OBJ entry. (In extended ACLs
  15  *    the ACL_MASK and ACL_GROUP_OBJ entries may differ.)
  16  *  - The identifier fields of the ACL_USER_OBJ and ACL_GROUP_OBJ
  17  *    entries contain the identifiers of the owner and owning group.
  18  *    (In POSIX ACLs we always set them to ACL_UNDEFINED_ID).
  19  *  - ACL entries in the kernel are kept sorted in ascending order
  20  *    of (e_tag, e_id). Solaris ACLs are unsorted.
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/fs.h>
  25 #include <linux/gfp.h>
  26 #include <linux/sunrpc/xdr.h>
  27 #include <linux/nfsacl.h>
  28 #include <linux/nfs3.h>
  29 #include <linux/sort.h>
  30
  31 MODULE_LICENSE("GPL");
  32
  33 EXPORT_SYMBOL_GPL(nfsacl_encode);
  34 EXPORT_SYMBOL_GPL(nfsacl_decode);
  35
  36 struct nfsacl_encode_desc {
  37         struct xdr_array2_desc desc;
  38         unsigned int count;
  39         struct posix_acl *acl;
  40         int typeflag;
  41         uid_t uid;
  42         gid_t gid;
  43 };
  44
  45 static int
  46 xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
  47 {
  48         struct nfsacl_encode_desc *nfsacl_desc =
  49                 (struct nfsacl_encode_desc *) desc;
  50         __be32 *p = elem;
  51
  52         struct posix_acl_entry *entry =
  53                 &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
  54
  55         *p++ = htonl(entry->e_tag | nfsacl_desc->typeflag);
  56         switch(entry->e_tag) {
  57                 case ACL_USER_OBJ:
  58                         *p++ = htonl(nfsacl_desc->uid);
  59                         break;
  60                 case ACL_GROUP_OBJ:
  61                         *p++ = htonl(nfsacl_desc->gid);
  62                         break;
  63                 case ACL_USER:
  64                 case ACL_GROUP:
  65                         *p++ = htonl(entry->e_id);
  66                         break;
  67                 default:  /* Solaris depends on that! */
  68                         *p++ = 0;
  69                         break;
  70         }
  71         *p++ = htonl(entry->e_perm & S_IRWXO);
  72         return 0;
  73 }
  74
  75 /**
  76  * nfsacl_encode - Encode an NFSv3 ACL
  77  *
  78  * @buf: destination xdr_buf to contain XDR encoded ACL
  79  * @base: byte offset in xdr_buf where XDR'd ACL begins
  80  * @inode: inode of file whose ACL this is
  81  * @acl: posix_acl to encode
  82  * @encode_entries: whether to encode ACEs as well
  83  * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
  84  *
  85  * Returns size of encoded ACL in bytes or a negative errno value.
  86  */
  87 int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
  88                   struct posix_acl *acl, int encode_entries, int typeflag)
  89 {
  90         int entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
  91         struct nfsacl_encode_desc nfsacl_desc = {
  92                 .desc = {
  93                         .elem_size = 12,
  94                         .array_len = encode_entries ? entries : 0,
  95                         .xcode = xdr_nfsace_encode,
  96                 },
  97                 .acl = acl,
  98                 .typeflag = typeflag,
  99                 .uid = inode->i_uid,
 100                 .gid = inode->i_gid,
 101         };
 102         int err;
 103         struct posix_acl *acl2 = NULL;
 104
 105         if (entries > NFS_ACL_MAX_ENTRIES ||
 106             xdr_encode_word(buf, base, entries))
 107                 return -EINVAL;
 108         if (encode_entries && acl && acl->a_count == 3) {
 109                 /* Fake up an ACL_MASK entry. */
 110                 acl2 = posix_acl_alloc(4, GFP_KERNEL);
 111                 if (!acl2)
 112                         return -ENOMEM;
 113                 /* Insert entries in canonical order: other orders seem
 114                  to confuse Solaris VxFS. */
 115                 acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
 116                 acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
 117                 acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
 118                 acl2->a_entries[2].e_tag = ACL_MASK;
 119                 acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
 120                 nfsacl_desc.acl = acl2;
 121         }
 122         err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
 123         if (acl2)
 124                 posix_acl_release(acl2);
 125         if (!err)
 126                 err = 8 + nfsacl_desc.desc.elem_size *
 127                           nfsacl_desc.desc.array_len;
 128         return err;
 129 }
 130
 131 struct nfsacl_decode_desc {
 132         struct xdr_array2_desc desc;
 133         unsigned int count;
 134         struct posix_acl *acl;
 135 };
 136
 137 static int
 138 xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
 139 {
 140         struct nfsacl_decode_desc *nfsacl_desc =
 141                 (struct nfsacl_decode_desc *) desc;
 142         __be32 *p = elem;
 143         struct posix_acl_entry *entry;
 144
 145         if (!nfsacl_desc->acl) {
 146                 if (desc->array_len > NFS_ACL_MAX_ENTRIES)
 147                         return -EINVAL;
 148                 nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
 149                 if (!nfsacl_desc->acl)
 150                         return -ENOMEM;
 151                 nfsacl_desc->count = 0;
 152         }
 153
 154         entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
 155         entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
 156         entry->e_id = ntohl(*p++);
 157         entry->e_perm = ntohl(*p++);
 158
 159         switch(entry->e_tag) {
 160                 case ACL_USER_OBJ:
 161                 case ACL_USER:
 162                 case ACL_GROUP_OBJ:
 163                 case ACL_GROUP:
 164                 case ACL_OTHER:
 165                         if (entry->e_perm & ~S_IRWXO)
 166                                 return -EINVAL;
 167                         break;
 168                 case ACL_MASK:
 169                         /* Solaris sometimes sets additonal bits in the mask */
 170                         entry->e_perm &= S_IRWXO;
 171                         break;
 172                 default:
 173                         return -EINVAL;
 174         }
 175
 176         return 0;
 177 }
 178
 179 static int
 180 cmp_acl_entry(const void *x, const void *y)
 181 {
 182         const struct posix_acl_entry *a = x, *b = y;
 183
 184         if (a->e_tag != b->e_tag)
 185                 return a->e_tag - b->e_tag;
 186         else if (a->e_id > b->e_id)
 187                 return 1;
 188         else if (a->e_id < b->e_id)
 189                 return -1;
 190         else
 191                 return 0;
 192 }
 193
 194 /*
 195  * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
 196  */
 197 static int
 198 posix_acl_from_nfsacl(struct posix_acl *acl)
 199 {
 200         struct posix_acl_entry *pa, *pe,
 201                *group_obj = NULL, *mask = NULL;
 202
 203         if (!acl)
 204                 return 0;
 205
 206         sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
 207              cmp_acl_entry, NULL);
 208
 209         /* Clear undefined identifier fields and find the ACL_GROUP_OBJ
 210            and ACL_MASK entries. */
 211         FOREACH_ACL_ENTRY(pa, acl, pe) {
 212                 switch(pa->e_tag) {
 213                         case ACL_USER_OBJ:
 214                                 pa->e_id = ACL_UNDEFINED_ID;
 215                                 break;
 216                         case ACL_GROUP_OBJ:
 217                                 pa->e_id = ACL_UNDEFINED_ID;
 218                                 group_obj = pa;
 219                                 break;
 220                         case ACL_MASK:
 221                                 mask = pa;
 222                                 /* fall through */
 223                         case ACL_OTHER:
 224                                 pa->e_id = ACL_UNDEFINED_ID;
 225                                 break;
 226                 }
 227         }
 228         if (acl->a_count == 4 && group_obj && mask &&
 229             mask->e_perm == group_obj->e_perm) {
 230                 /* remove bogus ACL_MASK entry */
 231                 memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
 232                                       sizeof(struct posix_acl_entry));
 233                 acl->a_count = 3;
 234         }
 235         return 0;
 236 }
 237
 238 /**
 239  * nfsacl_decode - Decode an NFSv3 ACL
 240  *
 241  * @buf: xdr_buf containing XDR'd ACL data to decode
 242  * @base: byte offset in xdr_buf where XDR'd ACL begins
 243  * @aclcnt: count of ACEs in decoded posix_acl
 244  * @pacl: buffer in which to place decoded posix_acl
 245  *
 246  * Returns the length of the decoded ACL in bytes, or a negative errno value.
 247  */
 248 int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
 249                   struct posix_acl **pacl)
 250 {
 251         struct nfsacl_decode_desc nfsacl_desc = {
 252                 .desc = {
 253                         .elem_size = 12,
 254                         .xcode = pacl ? xdr_nfsace_decode : NULL,
 255                 },
 256         };
 257         u32 entries;
 258         int err;
 259
 260         if (xdr_decode_word(buf, base, &entries) ||
 261             entries > NFS_ACL_MAX_ENTRIES)
 262                 return -EINVAL;
 263         nfsacl_desc.desc.array_maxlen = entries;
 264         err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
 265         if (err)
 266                 return err;
 267         if (pacl) {
 268                 if (entries != nfsacl_desc.desc.array_len ||
 269                     posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
 270                         posix_acl_release(nfsacl_desc.acl);
 271                         return -EINVAL;
 272                 }
 273                 *pacl = nfsacl_desc.acl;
 274         }
 275         if (aclcnt)
 276                 *aclcnt = entries;
 277         return 8 + nfsacl_desc.desc.elem_size *
 278                    nfsacl_desc.desc.array_len;
 279 }