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 struct nfsacl_simple_acl {
  46         struct posix_acl acl;
  47         struct posix_acl_entry ace[4];
  48 };
  49
  50 static int
  51 xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
  52 {
  53         struct nfsacl_encode_desc *nfsacl_desc =
  54                 (struct nfsacl_encode_desc *) desc;
  55         __be32 *p = elem;
  56
  57         struct posix_acl_entry *entry =
  58                 &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
  59
  60         *p++ = htonl(entry->e_tag | nfsacl_desc->typeflag);
  61         switch(entry->e_tag) {
  62                 case ACL_USER_OBJ:
  63                         *p++ = htonl(nfsacl_desc->uid);
  64                         break;
  65                 case ACL_GROUP_OBJ:
  66                         *p++ = htonl(nfsacl_desc->gid);
  67                         break;
  68                 case ACL_USER:
  69                 case ACL_GROUP:
  70                         *p++ = htonl(entry->e_id);
  71                         break;
  72                 default:  /* Solaris depends on that! */
  73                         *p++ = 0;
  74                         break;
  75         }
  76         *p++ = htonl(entry->e_perm & S_IRWXO);
  77         return 0;
  78 }
  79
  80 /**
  81  * nfsacl_encode - Encode an NFSv3 ACL
  82  *
  83  * @buf: destination xdr_buf to contain XDR encoded ACL
  84  * @base: byte offset in xdr_buf where XDR'd ACL begins
  85  * @inode: inode of file whose ACL this is
  86  * @acl: posix_acl to encode
  87  * @encode_entries: whether to encode ACEs as well
  88  * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
  89  *
  90  * Returns size of encoded ACL in bytes or a negative errno value.
  91  */
  92 int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
  93                   struct posix_acl *acl, int encode_entries, int typeflag)
  94 {
  95         int entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
  96         struct nfsacl_encode_desc nfsacl_desc = {
  97                 .desc = {
  98                         .elem_size = 12,
  99                         .array_len = encode_entries ? entries : 0,
 100                         .xcode = xdr_nfsace_encode,
 101                 },
 102                 .acl = acl,
 103                 .typeflag = typeflag,
 104                 .uid = inode->i_uid,
 105                 .gid = inode->i_gid,
 106         };
 107         struct nfsacl_simple_acl aclbuf;
 108         int err;
 109
 110         if (entries > NFS_ACL_MAX_ENTRIES ||
 111             xdr_encode_word(buf, base, entries))
 112                 return -EINVAL;
 113         if (encode_entries && acl && acl->a_count == 3) {
 114                 struct posix_acl *acl2 = &aclbuf.acl;
 115
 116                 /* Avoid the use of posix_acl_alloc().  nfsacl_encode() is
 117                  * invoked in contexts where a memory allocation failure is
 118                  * fatal.  Fortunately this fake ACL is small enough to
 119                  * construct on the stack. */
 120                 posix_acl_init(acl2, 4);
 121
 122                 /* Insert entries in canonical order: other orders seem
 123                  to confuse Solaris VxFS. */
 124                 acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
 125                 acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
 126                 acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
 127                 acl2->a_entries[2].e_tag = ACL_MASK;
 128                 acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
 129                 nfsacl_desc.acl = acl2;
 130         }
 131         err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
 132         if (!err)
 133                 err = 8 + nfsacl_desc.desc.elem_size *
 134                           nfsacl_desc.desc.array_len;
 135         return err;
 136 }
 137
 138 struct nfsacl_decode_desc {
 139         struct xdr_array2_desc desc;
 140         unsigned int count;
 141         struct posix_acl *acl;
 142 };
 143
 144 static int
 145 xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
 146 {
 147         struct nfsacl_decode_desc *nfsacl_desc =
 148                 (struct nfsacl_decode_desc *) desc;
 149         __be32 *p = elem;
 150         struct posix_acl_entry *entry;
 151
 152         if (!nfsacl_desc->acl) {
 153                 if (desc->array_len > NFS_ACL_MAX_ENTRIES)
 154                         return -EINVAL;
 155                 nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
 156                 if (!nfsacl_desc->acl)
 157                         return -ENOMEM;
 158                 nfsacl_desc->count = 0;
 159         }
 160
 161         entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
 162         entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
 163         entry->e_id = ntohl(*p++);
 164         entry->e_perm = ntohl(*p++);
 165
 166         switch(entry->e_tag) {
 167                 case ACL_USER_OBJ:
 168                 case ACL_USER:
 169                 case ACL_GROUP_OBJ:
 170                 case ACL_GROUP:
 171                 case ACL_OTHER:
 172                         if (entry->e_perm & ~S_IRWXO)
 173                                 return -EINVAL;
 174                         break;
 175                 case ACL_MASK:
 176                         /* Solaris sometimes sets additional bits in the mask */
 177                         entry->e_perm &= S_IRWXO;
 178                         break;
 179                 default:
 180                         return -EINVAL;
 181         }
 182
 183         return 0;
 184 }
 185
 186 static int
 187 cmp_acl_entry(const void *x, const void *y)
 188 {
 189         const struct posix_acl_entry *a = x, *b = y;
 190
 191         if (a->e_tag != b->e_tag)
 192                 return a->e_tag - b->e_tag;
 193         else if (a->e_id > b->e_id)
 194                 return 1;
 195         else if (a->e_id < b->e_id)
 196                 return -1;
 197         else
 198                 return 0;
 199 }
 200
 201 /*
 202  * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
 203  */
 204 static int
 205 posix_acl_from_nfsacl(struct posix_acl *acl)
 206 {
 207         struct posix_acl_entry *pa, *pe,
 208                *group_obj = NULL, *mask = NULL;
 209
 210         if (!acl)
 211                 return 0;
 212
 213         sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
 214              cmp_acl_entry, NULL);
 215
 216         /* Clear undefined identifier fields and find the ACL_GROUP_OBJ
 217            and ACL_MASK entries. */
 218         FOREACH_ACL_ENTRY(pa, acl, pe) {
 219                 switch(pa->e_tag) {
 220                         case ACL_USER_OBJ:
 221                                 pa->e_id = ACL_UNDEFINED_ID;
 222                                 break;
 223                         case ACL_GROUP_OBJ:
 224                                 pa->e_id = ACL_UNDEFINED_ID;
 225                                 group_obj = pa;
 226                                 break;
 227                         case ACL_MASK:
 228                                 mask = pa;
 229                                 /* fall through */
 230                         case ACL_OTHER:
 231                                 pa->e_id = ACL_UNDEFINED_ID;
 232                                 break;
 233                 }
 234         }
 235         if (acl->a_count == 4 && group_obj && mask &&
 236             mask->e_perm == group_obj->e_perm) {
 237                 /* remove bogus ACL_MASK entry */
 238                 memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
 239                                       sizeof(struct posix_acl_entry));
 240                 acl->a_count = 3;
 241         }
 242         return 0;
 243 }
 244
 245 /**
 246  * nfsacl_decode - Decode an NFSv3 ACL
 247  *
 248  * @buf: xdr_buf containing XDR'd ACL data to decode
 249  * @base: byte offset in xdr_buf where XDR'd ACL begins
 250  * @aclcnt: count of ACEs in decoded posix_acl
 251  * @pacl: buffer in which to place decoded posix_acl
 252  *
 253  * Returns the length of the decoded ACL in bytes, or a negative errno value.
 254  */
 255 int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
 256                   struct posix_acl **pacl)
 257 {
 258         struct nfsacl_decode_desc nfsacl_desc = {
 259                 .desc = {
 260                         .elem_size = 12,
 261                         .xcode = pacl ? xdr_nfsace_decode : NULL,
 262                 },
 263         };
 264         u32 entries;
 265         int err;
 266
 267         if (xdr_decode_word(buf, base, &entries) ||
 268             entries > NFS_ACL_MAX_ENTRIES)
 269                 return -EINVAL;
 270         nfsacl_desc.desc.array_maxlen = entries;
 271         err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
 272         if (err)
 273                 return err;
 274         if (pacl) {
 275                 if (entries != nfsacl_desc.desc.array_len ||
 276                     posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
 277                         posix_acl_release(nfsacl_desc.acl);
 278                         return -EINVAL;
 279                 }
 280                 *pacl = nfsacl_desc.acl;
 281         }
 282         if (aclcnt)
 283                 *aclcnt = entries;
 284         return 8 + nfsacl_desc.desc.elem_size *
 285                    nfsacl_desc.desc.array_len;
 286 }