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 struct nfsacl_encode_desc {
  34         struct xdr_array2_desc desc;
  35         unsigned int count;
  36         struct posix_acl *acl;
  37         int typeflag;
  38         kuid_t uid;
  39         kgid_t gid;
  40 };
  41
  42 struct nfsacl_simple_acl {
  43         struct posix_acl acl;
  44         struct posix_acl_entry ace[4];
  45 };
  46
  47 static int
  48 xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
  49 {
  50         struct nfsacl_encode_desc *nfsacl_desc =
  51                 (struct nfsacl_encode_desc *) desc;
  52         __be32 *p = elem;
  53
  54         struct posix_acl_entry *entry =
  55                 &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
  56
  57         *p++ = htonl(entry->e_tag | nfsacl_desc->typeflag);
  58         switch(entry->e_tag) {
  59                 case ACL_USER_OBJ:
  60                         *p++ = htonl(from_kuid(&init_user_ns, nfsacl_desc->uid));
  61                         break;
  62                 case ACL_GROUP_OBJ:
  63                         *p++ = htonl(from_kgid(&init_user_ns, nfsacl_desc->gid));
  64                         break;
  65                 case ACL_USER:
  66                         *p++ = htonl(from_kuid(&init_user_ns, entry->e_uid));
  67                         break;
  68                 case ACL_GROUP:
  69                         *p++ = htonl(from_kgid(&init_user_ns, entry->e_gid));
  70                         break;
  71                 default:  /* Solaris depends on that! */
  72                         *p++ = 0;
  73                         break;
  74         }
  75         *p++ = htonl(entry->e_perm & S_IRWXO);
  76         return 0;
  77 }
  78
  79 /**
  80  * nfsacl_encode - Encode an NFSv3 ACL
  81  *
  82  * @buf: destination xdr_buf to contain XDR encoded ACL
  83  * @base: byte offset in xdr_buf where XDR'd ACL begins
  84  * @inode: inode of file whose ACL this is
  85  * @acl: posix_acl to encode
  86  * @encode_entries: whether to encode ACEs as well
  87  * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
  88  *
  89  * Returns size of encoded ACL in bytes or a negative errno value.
  90  */
  91 int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
  92                   struct posix_acl *acl, int encode_entries, int typeflag)
  93 {
  94         int entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
  95         struct nfsacl_encode_desc nfsacl_desc = {
  96                 .desc = {
  97                         .elem_size = 12,
  98                         .array_len = encode_entries ? entries : 0,
  99                         .xcode = xdr_nfsace_encode,
 100                 },
 101                 .acl = acl,
 102                 .typeflag = typeflag,
 103                 .uid = inode->i_uid,
 104                 .gid = inode->i_gid,
 105         };
 106         struct nfsacl_simple_acl aclbuf;
 107         int err;
 108
 109         if (entries > NFS_ACL_MAX_ENTRIES ||
 110             xdr_encode_word(buf, base, entries))
 111                 return -EINVAL;
 112         if (encode_entries && acl && acl->a_count == 3) {
 113                 struct posix_acl *acl2 = &aclbuf.acl;
 114
 115                 /* Avoid the use of posix_acl_alloc().  nfsacl_encode() is
 116                  * invoked in contexts where a memory allocation failure is
 117                  * fatal.  Fortunately this fake ACL is small enough to
 118                  * construct on the stack. */
 119                 posix_acl_init(acl2, 4);
 120
 121                 /* Insert entries in canonical order: other orders seem
 122                  to confuse Solaris VxFS. */
 123                 acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
 124                 acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
 125                 acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
 126                 acl2->a_entries[2].e_tag = ACL_MASK;
 127                 acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
 128                 nfsacl_desc.acl = acl2;
 129         }
 130         err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
 131         if (!err)
 132                 err = 8 + nfsacl_desc.desc.elem_size *
 133                           nfsacl_desc.desc.array_len;
 134         return err;
 135 }
 136 EXPORT_SYMBOL_GPL(nfsacl_encode);
 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         unsigned int id;
 152
 153         if (!nfsacl_desc->acl) {
 154                 if (desc->array_len > NFS_ACL_MAX_ENTRIES)
 155                         return -EINVAL;
 156                 nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
 157                 if (!nfsacl_desc->acl)
 158                         return -ENOMEM;
 159                 nfsacl_desc->count = 0;
 160         }
 161
 162         entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
 163         entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
 164         id = ntohl(*p++);
 165         entry->e_perm = ntohl(*p++);
 166
 167         switch(entry->e_tag) {
 168                 case ACL_USER:
 169                         entry->e_uid = make_kuid(&init_user_ns, id);
 170                         if (!uid_valid(entry->e_uid))
 171                                 return -EINVAL;
 172                         break;
 173                 case ACL_GROUP:
 174                         entry->e_gid = make_kgid(&init_user_ns, id);
 175                         if (!gid_valid(entry->e_gid))
 176                                 return -EINVAL;
 177                         break;
 178                 case ACL_USER_OBJ:
 179                 case ACL_GROUP_OBJ:
 180                 case ACL_OTHER:
 181                         if (entry->e_perm & ~S_IRWXO)
 182                                 return -EINVAL;
 183                         break;
 184                 case ACL_MASK:
 185                         /* Solaris sometimes sets additional bits in the mask */
 186                         entry->e_perm &= S_IRWXO;
 187                         break;
 188                 default:
 189                         return -EINVAL;
 190         }
 191
 192         return 0;
 193 }
 194
 195 static int
 196 cmp_acl_entry(const void *x, const void *y)
 197 {
 198         const struct posix_acl_entry *a = x, *b = y;
 199
 200         if (a->e_tag != b->e_tag)
 201                 return a->e_tag - b->e_tag;
 202         else if ((a->e_tag == ACL_USER) && uid_gt(a->e_uid, b->e_uid))
 203                 return 1;
 204         else if ((a->e_tag == ACL_USER) && uid_lt(a->e_uid, b->e_uid))
 205                 return -1;
 206         else if ((a->e_tag == ACL_GROUP) && gid_gt(a->e_gid, b->e_gid))
 207                 return 1;
 208         else if ((a->e_tag == ACL_GROUP) && gid_lt(a->e_gid, b->e_gid))
 209                 return -1;
 210         else
 211                 return 0;
 212 }
 213
 214 /*
 215  * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
 216  */
 217 static int
 218 posix_acl_from_nfsacl(struct posix_acl *acl)
 219 {
 220         struct posix_acl_entry *pa, *pe,
 221                *group_obj = NULL, *mask = NULL;
 222
 223         if (!acl)
 224                 return 0;
 225
 226         sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
 227              cmp_acl_entry, NULL);
 228
 229         /* Find the ACL_GROUP_OBJ and ACL_MASK entries. */
 230         FOREACH_ACL_ENTRY(pa, acl, pe) {
 231                 switch(pa->e_tag) {
 232                         case ACL_USER_OBJ:
 233                                 break;
 234                         case ACL_GROUP_OBJ:
 235                                 group_obj = pa;
 236                                 break;
 237                         case ACL_MASK:
 238                                 mask = pa;
 239                                 /* fall through */
 240                         case ACL_OTHER:
 241                                 break;
 242                 }
 243         }
 244         if (acl->a_count == 4 && group_obj && mask &&
 245             mask->e_perm == group_obj->e_perm) {
 246                 /* remove bogus ACL_MASK entry */
 247                 memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
 248                                       sizeof(struct posix_acl_entry));
 249                 acl->a_count = 3;
 250         }
 251         return 0;
 252 }
 253
 254 /**
 255  * nfsacl_decode - Decode an NFSv3 ACL
 256  *
 257  * @buf: xdr_buf containing XDR'd ACL data to decode
 258  * @base: byte offset in xdr_buf where XDR'd ACL begins
 259  * @aclcnt: count of ACEs in decoded posix_acl
 260  * @pacl: buffer in which to place decoded posix_acl
 261  *
 262  * Returns the length of the decoded ACL in bytes, or a negative errno value.
 263  */
 264 int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
 265                   struct posix_acl **pacl)
 266 {
 267         struct nfsacl_decode_desc nfsacl_desc = {
 268                 .desc = {
 269                         .elem_size = 12,
 270                         .xcode = pacl ? xdr_nfsace_decode : NULL,
 271                 },
 272         };
 273         u32 entries;
 274         int err;
 275
 276         if (xdr_decode_word(buf, base, &entries) ||
 277             entries > NFS_ACL_MAX_ENTRIES)
 278                 return -EINVAL;
 279         nfsacl_desc.desc.array_maxlen = entries;
 280         err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
 281         if (err)
 282                 return err;
 283         if (pacl) {
 284                 if (entries != nfsacl_desc.desc.array_len ||
 285                     posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
 286                         posix_acl_release(nfsacl_desc.acl);
 287                         return -EINVAL;
 288                 }
 289                 *pacl = nfsacl_desc.acl;
 290         }
 291         if (aclcnt)
 292                 *aclcnt = entries;
 293         return 8 + nfsacl_desc.desc.elem_size *
 294                    nfsacl_desc.desc.array_len;
 295 }
 296 EXPORT_SYMBOL_GPL(nfsacl_decode);