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         kuid_t uid;
  42         kgid_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(from_kuid(&init_user_ns, nfsacl_desc->uid));
  64                         break;
  65                 case ACL_GROUP_OBJ:
  66                         *p++ = htonl(from_kgid(&init_user_ns, nfsacl_desc->gid));
  67                         break;
  68                 case ACL_USER:
  69                         *p++ = htonl(from_kuid(&init_user_ns, entry->e_uid));
  70                         break;
  71                 case ACL_GROUP:
  72                         *p++ = htonl(from_kgid(&init_user_ns, entry->e_gid));
  73                         break;
  74                 default:  /* Solaris depends on that! */
  75                         *p++ = 0;
  76                         break;
  77         }
  78         *p++ = htonl(entry->e_perm & S_IRWXO);
  79         return 0;
  80 }
  81
  82 /**
  83  * nfsacl_encode - Encode an NFSv3 ACL
  84  *
  85  * @buf: destination xdr_buf to contain XDR encoded ACL
  86  * @base: byte offset in xdr_buf where XDR'd ACL begins
  87  * @inode: inode of file whose ACL this is
  88  * @acl: posix_acl to encode
  89  * @encode_entries: whether to encode ACEs as well
  90  * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
  91  *
  92  * Returns size of encoded ACL in bytes or a negative errno value.
  93  */
  94 int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
  95                   struct posix_acl *acl, int encode_entries, int typeflag)
  96 {
  97         int entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
  98         struct nfsacl_encode_desc nfsacl_desc = {
  99                 .desc = {
 100                         .elem_size = 12,
 101                         .array_len = encode_entries ? entries : 0,
 102                         .xcode = xdr_nfsace_encode,
 103                 },
 104                 .acl = acl,
 105                 .typeflag = typeflag,
 106                 .uid = inode->i_uid,
 107                 .gid = inode->i_gid,
 108         };
 109         struct nfsacl_simple_acl aclbuf;
 110         int err;
 111
 112         if (entries > NFS_ACL_MAX_ENTRIES ||
 113             xdr_encode_word(buf, base, entries))
 114                 return -EINVAL;
 115         if (encode_entries && acl && acl->a_count == 3) {
 116                 struct posix_acl *acl2 = &aclbuf.acl;
 117
 118                 /* Avoid the use of posix_acl_alloc().  nfsacl_encode() is
 119                  * invoked in contexts where a memory allocation failure is
 120                  * fatal.  Fortunately this fake ACL is small enough to
 121                  * construct on the stack. */
 122                 posix_acl_init(acl2, 4);
 123
 124                 /* Insert entries in canonical order: other orders seem
 125                  to confuse Solaris VxFS. */
 126                 acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
 127                 acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
 128                 acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
 129                 acl2->a_entries[2].e_tag = ACL_MASK;
 130                 acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
 131                 nfsacl_desc.acl = acl2;
 132         }
 133         err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
 134         if (!err)
 135                 err = 8 + nfsacl_desc.desc.elem_size *
 136                           nfsacl_desc.desc.array_len;
 137         return err;
 138 }
 139
 140 struct nfsacl_decode_desc {
 141         struct xdr_array2_desc desc;
 142         unsigned int count;
 143         struct posix_acl *acl;
 144 };
 145
 146 static int
 147 xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
 148 {
 149         struct nfsacl_decode_desc *nfsacl_desc =
 150                 (struct nfsacl_decode_desc *) desc;
 151         __be32 *p = elem;
 152         struct posix_acl_entry *entry;
 153         unsigned int id;
 154
 155         if (!nfsacl_desc->acl) {
 156                 if (desc->array_len > NFS_ACL_MAX_ENTRIES)
 157                         return -EINVAL;
 158                 nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
 159                 if (!nfsacl_desc->acl)
 160                         return -ENOMEM;
 161                 nfsacl_desc->count = 0;
 162         }
 163
 164         entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
 165         entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
 166         id = ntohl(*p++);
 167         entry->e_perm = ntohl(*p++);
 168
 169         switch(entry->e_tag) {
 170                 case ACL_USER:
 171                         entry->e_uid = make_kuid(&init_user_ns, id);
 172                         if (!uid_valid(entry->e_uid))
 173                                 return -EINVAL;
 174                         break;
 175                 case ACL_GROUP:
 176                         entry->e_gid = make_kgid(&init_user_ns, id);
 177                         if (!gid_valid(entry->e_gid))
 178                                 return -EINVAL;
 179                         break;
 180                 case ACL_USER_OBJ:
 181                 case ACL_GROUP_OBJ:
 182                 case ACL_OTHER:
 183                         if (entry->e_perm & ~S_IRWXO)
 184                                 return -EINVAL;
 185                         break;
 186                 case ACL_MASK:
 187                         /* Solaris sometimes sets additional bits in the mask */
 188                         entry->e_perm &= S_IRWXO;
 189                         break;
 190                 default:
 191                         return -EINVAL;
 192         }
 193
 194         return 0;
 195 }
 196
 197 static int
 198 cmp_acl_entry(const void *x, const void *y)
 199 {
 200         const struct posix_acl_entry *a = x, *b = y;
 201
 202         if (a->e_tag != b->e_tag)
 203                 return a->e_tag - b->e_tag;
 204         else if ((a->e_tag == ACL_USER) && uid_gt(a->e_uid, b->e_uid))
 205                 return 1;
 206         else if ((a->e_tag == ACL_USER) && uid_lt(a->e_uid, b->e_uid))
 207                 return -1;
 208         else if ((a->e_tag == ACL_GROUP) && gid_gt(a->e_gid, b->e_gid))
 209                 return 1;
 210         else if ((a->e_tag == ACL_GROUP) && gid_lt(a->e_gid, b->e_gid))
 211                 return -1;
 212         else
 213                 return 0;
 214 }
 215
 216 /*
 217  * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
 218  */
 219 static int
 220 posix_acl_from_nfsacl(struct posix_acl *acl)
 221 {
 222         struct posix_acl_entry *pa, *pe,
 223                *group_obj = NULL, *mask = NULL;
 224
 225         if (!acl)
 226                 return 0;
 227
 228         sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
 229              cmp_acl_entry, NULL);
 230
 231         /* Find the ACL_GROUP_OBJ and ACL_MASK entries. */
 232         FOREACH_ACL_ENTRY(pa, acl, pe) {
 233                 switch(pa->e_tag) {
 234                         case ACL_USER_OBJ:
 235                                 break;
 236                         case ACL_GROUP_OBJ:
 237                                 group_obj = pa;
 238                                 break;
 239                         case ACL_MASK:
 240                                 mask = pa;
 241                                 /* fall through */
 242                         case ACL_OTHER:
 243                                 break;
 244                 }
 245         }
 246         if (acl->a_count == 4 && group_obj && mask &&
 247             mask->e_perm == group_obj->e_perm) {
 248                 /* remove bogus ACL_MASK entry */
 249                 memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
 250                                       sizeof(struct posix_acl_entry));
 251                 acl->a_count = 3;
 252         }
 253         return 0;
 254 }
 255
 256 /**
 257  * nfsacl_decode - Decode an NFSv3 ACL
 258  *
 259  * @buf: xdr_buf containing XDR'd ACL data to decode
 260  * @base: byte offset in xdr_buf where XDR'd ACL begins
 261  * @aclcnt: count of ACEs in decoded posix_acl
 262  * @pacl: buffer in which to place decoded posix_acl
 263  *
 264  * Returns the length of the decoded ACL in bytes, or a negative errno value.
 265  */
 266 int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
 267                   struct posix_acl **pacl)
 268 {
 269         struct nfsacl_decode_desc nfsacl_desc = {
 270                 .desc = {
 271                         .elem_size = 12,
 272                         .xcode = pacl ? xdr_nfsace_decode : NULL,
 273                 },
 274         };
 275         u32 entries;
 276         int err;
 277
 278         if (xdr_decode_word(buf, base, &entries) ||
 279             entries > NFS_ACL_MAX_ENTRIES)
 280                 return -EINVAL;
 281         nfsacl_desc.desc.array_maxlen = entries;
 282         err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
 283         if (err)
 284                 return err;
 285         if (pacl) {
 286                 if (entries != nfsacl_desc.desc.array_len ||
 287                     posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
 288                         posix_acl_release(nfsacl_desc.acl);
 289                         return -EINVAL;
 290                 }
 291                 *pacl = nfsacl_desc.acl;
 292         }
 293         if (aclcnt)
 294                 *aclcnt = entries;
 295         return 8 + nfsacl_desc.desc.elem_size *
 296                    nfsacl_desc.desc.array_len;
 297 }