fs/nfs_common/nfsacl.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * fs/nfs_common/nfsacl.c
   4  *
   5  *  Copyright (C) 2002-2003 Andreas Gruenbacher <agruen@suse.de>
   6  */
   7
   8 /*
   9  * The Solaris nfsacl protocol represents some ACLs slightly differently
  10  * than POSIX 1003.1e draft 17 does (and we do):
  11  *
  12  *  - Minimal ACLs always have an ACL_MASK entry, so they have
  13  *    four instead of three entries.
  14  *  - The ACL_MASK entry in such minimal ACLs always has the same
  15  *    permissions as the ACL_GROUP_OBJ entry. (In extended ACLs
  16  *    the ACL_MASK and ACL_GROUP_OBJ entries may differ.)
  17  *  - The identifier fields of the ACL_USER_OBJ and ACL_GROUP_OBJ
  18  *    entries contain the identifiers of the owner and owning group.
  19  *    (In POSIX ACLs we always set them to ACL_UNDEFINED_ID).
  20  *  - ACL entries in the kernel are kept sorted in ascending order
  21  *    of (e_tag, e_id). Solaris ACLs are unsorted.
  22  */
  23
  24 #include <linux/module.h>
  25 #include <linux/fs.h>
  26 #include <linux/gfp.h>
  27 #include <linux/sunrpc/xdr.h>
  28 #include <linux/nfsacl.h>
  29 #include <linux/nfs3.h>
  30 #include <linux/sort.h>
  31
  32 MODULE_DESCRIPTION("NFS ACL support");
  33 MODULE_LICENSE("GPL");
  34
  35 struct nfsacl_encode_desc {
  36         struct xdr_array2_desc desc;
  37         unsigned int count;
  38         struct posix_acl *acl;
  39         int typeflag;
  40         kuid_t uid;
  41         kgid_t gid;
  42 };
  43
  44 struct nfsacl_simple_acl {
  45         struct posix_acl acl;
  46         struct posix_acl_entry ace[4];
  47 };
  48
  49 static int
  50 xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
  51 {
  52         struct nfsacl_encode_desc *nfsacl_desc =
  53                 (struct nfsacl_encode_desc *) desc;
  54         __be32 *p = elem;
  55
  56         struct posix_acl_entry *entry =
  57                 &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
  58
  59         *p++ = htonl(entry->e_tag | nfsacl_desc->typeflag);
  60         switch(entry->e_tag) {
  61                 case ACL_USER_OBJ:
  62                         *p++ = htonl(from_kuid(&init_user_ns, nfsacl_desc->uid));
  63                         break;
  64                 case ACL_GROUP_OBJ:
  65                         *p++ = htonl(from_kgid(&init_user_ns, nfsacl_desc->gid));
  66                         break;
  67                 case ACL_USER:
  68                         *p++ = htonl(from_kuid(&init_user_ns, entry->e_uid));
  69                         break;
  70                 case ACL_GROUP:
  71                         *p++ = htonl(from_kgid(&init_user_ns, entry->e_gid));
  72                         break;
  73                 default:  /* Solaris depends on that! */
  74                         *p++ = 0;
  75                         break;
  76         }
  77         *p++ = htonl(entry->e_perm & S_IRWXO);
  78         return 0;
  79 }
  80
  81 /**
  82  * nfsacl_encode - Encode an NFSv3 ACL
  83  *
  84  * @buf: destination xdr_buf to contain XDR encoded ACL
  85  * @base: byte offset in xdr_buf where XDR'd ACL begins
  86  * @inode: inode of file whose ACL this is
  87  * @acl: posix_acl to encode
  88  * @encode_entries: whether to encode ACEs as well
  89  * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
  90  *
  91  * Returns size of encoded ACL in bytes or a negative errno value.
  92  */
  93 int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
  94                   struct posix_acl *acl, int encode_entries, int typeflag)
  95 {
  96         int entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
  97         struct nfsacl_encode_desc nfsacl_desc = {
  98                 .desc = {
  99                         .elem_size = 12,
 100                         .array_len = encode_entries ? entries : 0,
 101                         .xcode = xdr_nfsace_encode,
 102                 },
 103                 .acl = acl,
 104                 .typeflag = typeflag,
 105                 .uid = inode->i_uid,
 106                 .gid = inode->i_gid,
 107         };
 108         struct nfsacl_simple_acl aclbuf;
 109         int err;
 110
 111         if (entries > NFS_ACL_MAX_ENTRIES ||
 112             xdr_encode_word(buf, base, entries))
 113                 return -EINVAL;
 114         if (encode_entries && acl && acl->a_count == 3) {
 115                 struct posix_acl *acl2 = &aclbuf.acl;
 116
 117                 /* Avoid the use of posix_acl_alloc().  nfsacl_encode() is
 118                  * invoked in contexts where a memory allocation failure is
 119                  * fatal.  Fortunately this fake ACL is small enough to
 120                  * construct on the stack. */
 121                 posix_acl_init(acl2, 4);
 122
 123                 /* Insert entries in canonical order: other orders seem
 124                  to confuse Solaris VxFS. */
 125                 acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
 126                 acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
 127                 acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
 128                 acl2->a_entries[2].e_tag = ACL_MASK;
 129                 acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
 130                 nfsacl_desc.acl = acl2;
 131         }
 132         err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
 133         if (!err)
 134                 err = 8 + nfsacl_desc.desc.elem_size *
 135                           nfsacl_desc.desc.array_len;
 136         return err;
 137 }
 138 EXPORT_SYMBOL_GPL(nfsacl_encode);
 139
 140 /**
 141  * nfs_stream_encode_acl - Encode an NFSv3 ACL
 142  *
 143  * @xdr: an xdr_stream positioned to receive an encoded ACL
 144  * @inode: inode of file whose ACL this is
 145  * @acl: posix_acl to encode
 146  * @encode_entries: whether to encode ACEs as well
 147  * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
 148  *
 149  * Return values:
 150  *   %false: The ACL could not be encoded
 151  *   %true: @xdr is advanced to the next available position
 152  */
 153 bool nfs_stream_encode_acl(struct xdr_stream *xdr, struct inode *inode,
 154                            struct posix_acl *acl, int encode_entries,
 155                            int typeflag)
 156 {
 157         const size_t elem_size = XDR_UNIT * 3;
 158         u32 entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
 159         struct nfsacl_encode_desc nfsacl_desc = {
 160                 .desc = {
 161                         .elem_size = elem_size,
 162                         .array_len = encode_entries ? entries : 0,
 163                         .xcode = xdr_nfsace_encode,
 164                 },
 165                 .acl = acl,
 166                 .typeflag = typeflag,
 167                 .uid = inode->i_uid,
 168                 .gid = inode->i_gid,
 169         };
 170         struct nfsacl_simple_acl aclbuf;
 171         unsigned int base;
 172         int err;
 173
 174         if (entries > NFS_ACL_MAX_ENTRIES)
 175                 return false;
 176         if (xdr_stream_encode_u32(xdr, entries) < 0)
 177                 return false;
 178
 179         if (encode_entries && acl && acl->a_count == 3) {
 180                 struct posix_acl *acl2 = &aclbuf.acl;
 181
 182                 /* Avoid the use of posix_acl_alloc().  nfsacl_encode() is
 183                  * invoked in contexts where a memory allocation failure is
 184                  * fatal.  Fortunately this fake ACL is small enough to
 185                  * construct on the stack. */
 186                 posix_acl_init(acl2, 4);
 187
 188                 /* Insert entries in canonical order: other orders seem
 189                  to confuse Solaris VxFS. */
 190                 acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
 191                 acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
 192                 acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
 193                 acl2->a_entries[2].e_tag = ACL_MASK;
 194                 acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
 195                 nfsacl_desc.acl = acl2;
 196         }
 197
 198         base = xdr_stream_pos(xdr);
 199         if (!xdr_reserve_space(xdr, XDR_UNIT +
 200                                elem_size * nfsacl_desc.desc.array_len))
 201                 return false;
 202         err = xdr_encode_array2(xdr->buf, base, &nfsacl_desc.desc);
 203         if (err)
 204                 return false;
 205
 206         return true;
 207 }
 208 EXPORT_SYMBOL_GPL(nfs_stream_encode_acl);
 209
 210
 211 struct nfsacl_decode_desc {
 212         struct xdr_array2_desc desc;
 213         unsigned int count;
 214         struct posix_acl *acl;
 215 };
 216
 217 static int
 218 xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
 219 {
 220         struct nfsacl_decode_desc *nfsacl_desc =
 221                 (struct nfsacl_decode_desc *) desc;
 222         __be32 *p = elem;
 223         struct posix_acl_entry *entry;
 224         unsigned int id;
 225
 226         if (!nfsacl_desc->acl) {
 227                 if (desc->array_len > NFS_ACL_MAX_ENTRIES)
 228                         return -EINVAL;
 229                 nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
 230                 if (!nfsacl_desc->acl)
 231                         return -ENOMEM;
 232                 nfsacl_desc->count = 0;
 233         }
 234
 235         entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
 236         entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
 237         id = ntohl(*p++);
 238         entry->e_perm = ntohl(*p++);
 239
 240         switch(entry->e_tag) {
 241                 case ACL_USER:
 242                         entry->e_uid = make_kuid(&init_user_ns, id);
 243                         if (!uid_valid(entry->e_uid))
 244                                 return -EINVAL;
 245                         break;
 246                 case ACL_GROUP:
 247                         entry->e_gid = make_kgid(&init_user_ns, id);
 248                         if (!gid_valid(entry->e_gid))
 249                                 return -EINVAL;
 250                         break;
 251                 case ACL_USER_OBJ:
 252                 case ACL_GROUP_OBJ:
 253                 case ACL_OTHER:
 254                         if (entry->e_perm & ~S_IRWXO)
 255                                 return -EINVAL;
 256                         break;
 257                 case ACL_MASK:
 258                         /* Solaris sometimes sets additional bits in the mask */
 259                         entry->e_perm &= S_IRWXO;
 260                         break;
 261                 default:
 262                         return -EINVAL;
 263         }
 264
 265         return 0;
 266 }
 267
 268 static int
 269 cmp_acl_entry(const void *x, const void *y)
 270 {
 271         const struct posix_acl_entry *a = x, *b = y;
 272
 273         if (a->e_tag != b->e_tag)
 274                 return a->e_tag - b->e_tag;
 275         else if ((a->e_tag == ACL_USER) && uid_gt(a->e_uid, b->e_uid))
 276                 return 1;
 277         else if ((a->e_tag == ACL_USER) && uid_lt(a->e_uid, b->e_uid))
 278                 return -1;
 279         else if ((a->e_tag == ACL_GROUP) && gid_gt(a->e_gid, b->e_gid))
 280                 return 1;
 281         else if ((a->e_tag == ACL_GROUP) && gid_lt(a->e_gid, b->e_gid))
 282                 return -1;
 283         else
 284                 return 0;
 285 }
 286
 287 /*
 288  * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
 289  */
 290 static int
 291 posix_acl_from_nfsacl(struct posix_acl *acl)
 292 {
 293         struct posix_acl_entry *pa, *pe,
 294                *group_obj = NULL, *mask = NULL;
 295
 296         if (!acl)
 297                 return 0;
 298
 299         sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
 300              cmp_acl_entry, NULL);
 301
 302         /* Find the ACL_GROUP_OBJ and ACL_MASK entries. */
 303         FOREACH_ACL_ENTRY(pa, acl, pe) {
 304                 switch(pa->e_tag) {
 305                         case ACL_USER_OBJ:
 306                                 break;
 307                         case ACL_GROUP_OBJ:
 308                                 group_obj = pa;
 309                                 break;
 310                         case ACL_MASK:
 311                                 mask = pa;
 312                                 fallthrough;
 313                         case ACL_OTHER:
 314                                 break;
 315                 }
 316         }
 317         if (acl->a_count == 4 && group_obj && mask &&
 318             mask->e_perm == group_obj->e_perm) {
 319                 /* remove bogus ACL_MASK entry */
 320                 memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
 321                                       sizeof(struct posix_acl_entry));
 322                 acl->a_count = 3;
 323         }
 324         return 0;
 325 }
 326
 327 /**
 328  * nfsacl_decode - Decode an NFSv3 ACL
 329  *
 330  * @buf: xdr_buf containing XDR'd ACL data to decode
 331  * @base: byte offset in xdr_buf where XDR'd ACL begins
 332  * @aclcnt: count of ACEs in decoded posix_acl
 333  * @pacl: buffer in which to place decoded posix_acl
 334  *
 335  * Returns the length of the decoded ACL in bytes, or a negative errno value.
 336  */
 337 int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
 338                   struct posix_acl **pacl)
 339 {
 340         struct nfsacl_decode_desc nfsacl_desc = {
 341                 .desc = {
 342                         .elem_size = 12,
 343                         .xcode = pacl ? xdr_nfsace_decode : NULL,
 344                 },
 345         };
 346         u32 entries;
 347         int err;
 348
 349         if (xdr_decode_word(buf, base, &entries) ||
 350             entries > NFS_ACL_MAX_ENTRIES)
 351                 return -EINVAL;
 352         nfsacl_desc.desc.array_maxlen = entries;
 353         err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
 354         if (err)
 355                 return err;
 356         if (pacl) {
 357                 if (entries != nfsacl_desc.desc.array_len ||
 358                     posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
 359                         posix_acl_release(nfsacl_desc.acl);
 360                         return -EINVAL;
 361                 }
 362                 *pacl = nfsacl_desc.acl;
 363         }
 364         if (aclcnt)
 365                 *aclcnt = entries;
 366         return 8 + nfsacl_desc.desc.elem_size *
 367                    nfsacl_desc.desc.array_len;
 368 }
 369 EXPORT_SYMBOL_GPL(nfsacl_decode);
 370
 371 /**
 372  * nfs_stream_decode_acl - Decode an NFSv3 ACL
 373  *
 374  * @xdr: an xdr_stream positioned at an encoded ACL
 375  * @aclcnt: OUT: count of ACEs in decoded posix_acl
 376  * @pacl: OUT: a dynamically-allocated buffer containing the decoded posix_acl
 377  *
 378  * Return values:
 379  *   %false: The encoded ACL is not valid
 380  *   %true: @pacl contains a decoded ACL, and @xdr is advanced
 381  *
 382  * On a successful return, caller must release *pacl using posix_acl_release().
 383  */
 384 bool nfs_stream_decode_acl(struct xdr_stream *xdr, unsigned int *aclcnt,
 385                            struct posix_acl **pacl)
 386 {
 387         const size_t elem_size = XDR_UNIT * 3;
 388         struct nfsacl_decode_desc nfsacl_desc = {
 389                 .desc = {
 390                         .elem_size = elem_size,
 391                         .xcode = pacl ? xdr_nfsace_decode : NULL,
 392                 },
 393         };
 394         unsigned int base;
 395         u32 entries;
 396
 397         if (xdr_stream_decode_u32(xdr, &entries) < 0)
 398                 return false;
 399         if (entries > NFS_ACL_MAX_ENTRIES)
 400                 return false;
 401
 402         base = xdr_stream_pos(xdr);
 403         if (!xdr_inline_decode(xdr, XDR_UNIT + elem_size * entries))
 404                 return false;
 405         nfsacl_desc.desc.array_maxlen = entries;
 406         if (xdr_decode_array2(xdr->buf, base, &nfsacl_desc.desc))
 407                 return false;
 408
 409         if (pacl) {
 410                 if (entries != nfsacl_desc.desc.array_len ||
 411                     posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
 412                         posix_acl_release(nfsacl_desc.acl);
 413                         return false;
 414                 }
 415                 *pacl = nfsacl_desc.acl;
 416         }
 417         if (aclcnt)
 418                 *aclcnt = entries;
 419         return true;
 420 }
 421 EXPORT_SYMBOL_GPL(nfs_stream_decode_acl);