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Linux/fs/nfs_common/nfsacl.c

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  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);
297 

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