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_LICENSE("GPL");
  33
  34 struct nfsacl_encode_desc {
  35         struct xdr_array2_desc desc;
  36         unsigned int count;
  37         struct posix_acl *acl;
  38         int typeflag;
  39         kuid_t uid;
  40         kgid_t gid;
  41 };
  42
  43 struct nfsacl_simple_acl {
  44         struct posix_acl acl;
  45         struct posix_acl_entry ace[4];
  46 };
  47
  48 static int
  49 xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
  50 {
  51         struct nfsacl_encode_desc *nfsacl_desc =
  52                 (struct nfsacl_encode_desc *) desc;
  53         __be32 *p = elem;
  54
  55         struct posix_acl_entry *entry =
  56                 &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
  57
  58         *p++ = htonl(entry->e_tag | nfsacl_desc->typeflag);
  59         switch(entry->e_tag) {
  60                 case ACL_USER_OBJ:
  61                         *p++ = htonl(from_kuid(&init_user_ns, nfsacl_desc->uid));
  62                         break;
  63                 case ACL_GROUP_OBJ:
  64                         *p++ = htonl(from_kgid(&init_user_ns, nfsacl_desc->gid));
  65                         break;
  66                 case ACL_USER:
  67                         *p++ = htonl(from_kuid(&init_user_ns, entry->e_uid));
  68                         break;
  69                 case ACL_GROUP:
  70                         *p++ = htonl(from_kgid(&init_user_ns, entry->e_gid));
  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 EXPORT_SYMBOL_GPL(nfsacl_encode);
 138
 139 struct nfsacl_decode_desc {
 140         struct xdr_array2_desc desc;
 141         unsigned int count;
 142         struct posix_acl *acl;
 143 };
 144
 145 static int
 146 xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
 147 {
 148         struct nfsacl_decode_desc *nfsacl_desc =
 149                 (struct nfsacl_decode_desc *) desc;
 150         __be32 *p = elem;
 151         struct posix_acl_entry *entry;
 152         unsigned int id;
 153
 154         if (!nfsacl_desc->acl) {
 155                 if (desc->array_len > NFS_ACL_MAX_ENTRIES)
 156                         return -EINVAL;
 157                 nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
 158                 if (!nfsacl_desc->acl)
 159                         return -ENOMEM;
 160                 nfsacl_desc->count = 0;
 161         }
 162
 163         entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
 164         entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
 165         id = ntohl(*p++);
 166         entry->e_perm = ntohl(*p++);
 167
 168         switch(entry->e_tag) {
 169                 case ACL_USER:
 170                         entry->e_uid = make_kuid(&init_user_ns, id);
 171                         if (!uid_valid(entry->e_uid))
 172                                 return -EINVAL;
 173                         break;
 174                 case ACL_GROUP:
 175                         entry->e_gid = make_kgid(&init_user_ns, id);
 176                         if (!gid_valid(entry->e_gid))
 177                                 return -EINVAL;
 178                         break;
 179                 case ACL_USER_OBJ:
 180                 case ACL_GROUP_OBJ:
 181                 case ACL_OTHER:
 182                         if (entry->e_perm & ~S_IRWXO)
 183                                 return -EINVAL;
 184                         break;
 185                 case ACL_MASK:
 186                         /* Solaris sometimes sets additional bits in the mask */
 187                         entry->e_perm &= S_IRWXO;
 188                         break;
 189                 default:
 190                         return -EINVAL;
 191         }
 192
 193         return 0;
 194 }
 195
 196 static int
 197 cmp_acl_entry(const void *x, const void *y)
 198 {
 199         const struct posix_acl_entry *a = x, *b = y;
 200
 201         if (a->e_tag != b->e_tag)
 202                 return a->e_tag - b->e_tag;
 203         else if ((a->e_tag == ACL_USER) && uid_gt(a->e_uid, b->e_uid))
 204                 return 1;
 205         else if ((a->e_tag == ACL_USER) && uid_lt(a->e_uid, b->e_uid))
 206                 return -1;
 207         else if ((a->e_tag == ACL_GROUP) && gid_gt(a->e_gid, b->e_gid))
 208                 return 1;
 209         else if ((a->e_tag == ACL_GROUP) && gid_lt(a->e_gid, b->e_gid))
 210                 return -1;
 211         else
 212                 return 0;
 213 }
 214
 215 /*
 216  * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
 217  */
 218 static int
 219 posix_acl_from_nfsacl(struct posix_acl *acl)
 220 {
 221         struct posix_acl_entry *pa, *pe,
 222                *group_obj = NULL, *mask = NULL;
 223
 224         if (!acl)
 225                 return 0;
 226
 227         sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
 228              cmp_acl_entry, NULL);
 229
 230         /* Find the ACL_GROUP_OBJ and ACL_MASK entries. */
 231         FOREACH_ACL_ENTRY(pa, acl, pe) {
 232                 switch(pa->e_tag) {
 233                         case ACL_USER_OBJ:
 234                                 break;
 235                         case ACL_GROUP_OBJ:
 236                                 group_obj = pa;
 237                                 break;
 238                         case ACL_MASK:
 239                                 mask = pa;
 240                                 fallthrough;
 241                         case ACL_OTHER:
 242                                 break;
 243                 }
 244         }
 245         if (acl->a_count == 4 && group_obj && mask &&
 246             mask->e_perm == group_obj->e_perm) {
 247                 /* remove bogus ACL_MASK entry */
 248                 memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
 249                                       sizeof(struct posix_acl_entry));
 250                 acl->a_count = 3;
 251         }
 252         return 0;
 253 }
 254
 255 /**
 256  * nfsacl_decode - Decode an NFSv3 ACL
 257  *
 258  * @buf: xdr_buf containing XDR'd ACL data to decode
 259  * @base: byte offset in xdr_buf where XDR'd ACL begins
 260  * @aclcnt: count of ACEs in decoded posix_acl
 261  * @pacl: buffer in which to place decoded posix_acl
 262  *
 263  * Returns the length of the decoded ACL in bytes, or a negative errno value.
 264  */
 265 int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
 266                   struct posix_acl **pacl)
 267 {
 268         struct nfsacl_decode_desc nfsacl_desc = {
 269                 .desc = {
 270                         .elem_size = 12,
 271                         .xcode = pacl ? xdr_nfsace_decode : NULL,
 272                 },
 273         };
 274         u32 entries;
 275         int err;
 276
 277         if (xdr_decode_word(buf, base, &entries) ||
 278             entries > NFS_ACL_MAX_ENTRIES)
 279                 return -EINVAL;
 280         nfsacl_desc.desc.array_maxlen = entries;
 281         err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
 282         if (err)
 283                 return err;
 284         if (pacl) {
 285                 if (entries != nfsacl_desc.desc.array_len ||
 286                     posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
 287                         posix_acl_release(nfsacl_desc.acl);
 288                         return -EINVAL;
 289                 }
 290                 *pacl = nfsacl_desc.acl;
 291         }
 292         if (aclcnt)
 293                 *aclcnt = entries;
 294         return 8 + nfsacl_desc.desc.elem_size *
 295                    nfsacl_desc.desc.array_len;
 296 }
 297 EXPORT_SYMBOL_GPL(nfsacl_decode);