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
 32MODULE_DESCRIPTION("NFS ACL support");
 33MODULE_LICENSE("GPL");
 34
 35struct 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
 44struct nfsacl_simple_acl {
 45	struct posix_acl_hdr acl;
 46	struct posix_acl_entry ace[4];
 47};
 48
 49static int
 50xdr_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 */
 93int 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 =
116			container_of(&aclbuf.acl, struct posix_acl, hdr);
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}
139EXPORT_SYMBOL_GPL(nfsacl_encode);
140
141/**
142 * nfs_stream_encode_acl - Encode an NFSv3 ACL
143 *
144 * @xdr: an xdr_stream positioned to receive an encoded ACL
145 * @inode: inode of file whose ACL this is
146 * @acl: posix_acl to encode
147 * @encode_entries: whether to encode ACEs as well
148 * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
149 *
150 * Return values:
151 *   %false: The ACL could not be encoded
152 *   %true: @xdr is advanced to the next available position
153 */
154bool nfs_stream_encode_acl(struct xdr_stream *xdr, struct inode *inode,
155			   struct posix_acl *acl, int encode_entries,
156			   int typeflag)
157{
158	const size_t elem_size = XDR_UNIT * 3;
159	u32 entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
160	struct nfsacl_encode_desc nfsacl_desc = {
161		.desc = {
162			.elem_size = elem_size,
163			.array_len = encode_entries ? entries : 0,
164			.xcode = xdr_nfsace_encode,
165		},
166		.acl = acl,
167		.typeflag = typeflag,
168		.uid = inode->i_uid,
169		.gid = inode->i_gid,
170	};
171	struct nfsacl_simple_acl aclbuf;
172	unsigned int base;
173	int err;
174
175	if (entries > NFS_ACL_MAX_ENTRIES)
176		return false;
177	if (xdr_stream_encode_u32(xdr, entries) < 0)
178		return false;
179
180	if (encode_entries && acl && acl->a_count == 3) {
181		struct posix_acl *acl2 =
182			container_of(&aclbuf.acl, struct posix_acl, hdr);
183
184		/* Avoid the use of posix_acl_alloc().  nfsacl_encode() is
185		 * invoked in contexts where a memory allocation failure is
186		 * fatal.  Fortunately this fake ACL is small enough to
187		 * construct on the stack. */
188		posix_acl_init(acl2, 4);
189
190		/* Insert entries in canonical order: other orders seem
191		 to confuse Solaris VxFS. */
192		acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
193		acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
194		acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
195		acl2->a_entries[2].e_tag = ACL_MASK;
196		acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
197		nfsacl_desc.acl = acl2;
198	}
199
200	base = xdr_stream_pos(xdr);
201	if (!xdr_reserve_space(xdr, XDR_UNIT +
202			       elem_size * nfsacl_desc.desc.array_len))
203		return false;
204	err = xdr_encode_array2(xdr->buf, base, &nfsacl_desc.desc);
205	if (err)
206		return false;
207
208	return true;
209}
210EXPORT_SYMBOL_GPL(nfs_stream_encode_acl);
211
212
213struct nfsacl_decode_desc {
214	struct xdr_array2_desc desc;
215	unsigned int count;
216	struct posix_acl *acl;
217};
218
219static int
220xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
221{
222	struct nfsacl_decode_desc *nfsacl_desc =
223		(struct nfsacl_decode_desc *) desc;
224	__be32 *p = elem;
225	struct posix_acl_entry *entry;
226	unsigned int id;
227
228	if (!nfsacl_desc->acl) {
229		if (desc->array_len > NFS_ACL_MAX_ENTRIES)
230			return -EINVAL;
231		nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
232		if (!nfsacl_desc->acl)
233			return -ENOMEM;
234		nfsacl_desc->count = 0;
235	}
236
237	entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
238	entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
239	id = ntohl(*p++);
240	entry->e_perm = ntohl(*p++);
241
242	switch(entry->e_tag) {
243		case ACL_USER:
244			entry->e_uid = make_kuid(&init_user_ns, id);
245			if (!uid_valid(entry->e_uid))
246				return -EINVAL;
247			break;
248		case ACL_GROUP:
249			entry->e_gid = make_kgid(&init_user_ns, id);
250			if (!gid_valid(entry->e_gid))
251				return -EINVAL;
252			break;
253		case ACL_USER_OBJ:
254		case ACL_GROUP_OBJ:
255		case ACL_OTHER:
256			if (entry->e_perm & ~S_IRWXO)
257				return -EINVAL;
258			break;
259		case ACL_MASK:
260			/* Solaris sometimes sets additional bits in the mask */
261			entry->e_perm &= S_IRWXO;
262			break;
263		default:
264			return -EINVAL;
265	}
266
267	return 0;
268}
269
270static int
271cmp_acl_entry(const void *x, const void *y)
272{
273	const struct posix_acl_entry *a = x, *b = y;
274
275	if (a->e_tag != b->e_tag)
276		return a->e_tag - b->e_tag;
277	else if ((a->e_tag == ACL_USER) && uid_gt(a->e_uid, b->e_uid))
278		return 1;
279	else if ((a->e_tag == ACL_USER) && uid_lt(a->e_uid, b->e_uid))
280		return -1;
281	else if ((a->e_tag == ACL_GROUP) && gid_gt(a->e_gid, b->e_gid))
282		return 1;
283	else if ((a->e_tag == ACL_GROUP) && gid_lt(a->e_gid, b->e_gid))
284		return -1;
285	else
286		return 0;
287}
288
289/*
290 * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
291 */
292static int
293posix_acl_from_nfsacl(struct posix_acl *acl)
294{
295	struct posix_acl_entry *pa, *pe,
296	       *group_obj = NULL, *mask = NULL;
297
298	if (!acl)
299		return 0;
300
301	sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
302	     cmp_acl_entry, NULL);
303
304	/* Find the ACL_GROUP_OBJ and ACL_MASK entries. */
305	FOREACH_ACL_ENTRY(pa, acl, pe) {
306		switch(pa->e_tag) {
307			case ACL_USER_OBJ:
308				break;
309			case ACL_GROUP_OBJ:
310				group_obj = pa;
311				break;
312			case ACL_MASK:
313				mask = pa;
314				fallthrough;
315			case ACL_OTHER:
316				break;
317		}
318	}
319	if (acl->a_count == 4 && group_obj && mask &&
320	    mask->e_perm == group_obj->e_perm) {
321		/* remove bogus ACL_MASK entry */
322		memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
323				      sizeof(struct posix_acl_entry));
324		acl->a_count = 3;
325	}
326	return 0;
327}
328
329/**
330 * nfsacl_decode - Decode an NFSv3 ACL
331 *
332 * @buf: xdr_buf containing XDR'd ACL data to decode
333 * @base: byte offset in xdr_buf where XDR'd ACL begins
334 * @aclcnt: count of ACEs in decoded posix_acl
335 * @pacl: buffer in which to place decoded posix_acl
336 *
337 * Returns the length of the decoded ACL in bytes, or a negative errno value.
338 */
339int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
340		  struct posix_acl **pacl)
341{
342	struct nfsacl_decode_desc nfsacl_desc = {
343		.desc = {
344			.elem_size = 12,
345			.xcode = pacl ? xdr_nfsace_decode : NULL,
346		},
347	};
348	u32 entries;
349	int err;
350
351	if (xdr_decode_word(buf, base, &entries) ||
352	    entries > NFS_ACL_MAX_ENTRIES)
353		return -EINVAL;
354	nfsacl_desc.desc.array_maxlen = entries;
355	err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
356	if (err)
357		return err;
358	if (pacl) {
359		if (entries != nfsacl_desc.desc.array_len ||
360		    posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
361			posix_acl_release(nfsacl_desc.acl);
362			return -EINVAL;
363		}
364		*pacl = nfsacl_desc.acl;
365	}
366	if (aclcnt)
367		*aclcnt = entries;
368	return 8 + nfsacl_desc.desc.elem_size *
369		   nfsacl_desc.desc.array_len;
370}
371EXPORT_SYMBOL_GPL(nfsacl_decode);
372
373/**
374 * nfs_stream_decode_acl - Decode an NFSv3 ACL
375 *
376 * @xdr: an xdr_stream positioned at an encoded ACL
377 * @aclcnt: OUT: count of ACEs in decoded posix_acl
378 * @pacl: OUT: a dynamically-allocated buffer containing the decoded posix_acl
379 *
380 * Return values:
381 *   %false: The encoded ACL is not valid
382 *   %true: @pacl contains a decoded ACL, and @xdr is advanced
383 *
384 * On a successful return, caller must release *pacl using posix_acl_release().
385 */
386bool nfs_stream_decode_acl(struct xdr_stream *xdr, unsigned int *aclcnt,
387			   struct posix_acl **pacl)
388{
389	const size_t elem_size = XDR_UNIT * 3;
390	struct nfsacl_decode_desc nfsacl_desc = {
391		.desc = {
392			.elem_size = elem_size,
393			.xcode = pacl ? xdr_nfsace_decode : NULL,
394		},
395	};
396	unsigned int base;
397	u32 entries;
398
399	if (xdr_stream_decode_u32(xdr, &entries) < 0)
400		return false;
401	if (entries > NFS_ACL_MAX_ENTRIES)
402		return false;
403
404	base = xdr_stream_pos(xdr);
405	if (!xdr_inline_decode(xdr, XDR_UNIT + elem_size * entries))
406		return false;
407	nfsacl_desc.desc.array_maxlen = entries;
408	if (xdr_decode_array2(xdr->buf, base, &nfsacl_desc.desc))
409		return false;
410
411	if (pacl) {
412		if (entries != nfsacl_desc.desc.array_len ||
413		    posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
414			posix_acl_release(nfsacl_desc.acl);
415			return false;
416		}
417		*pacl = nfsacl_desc.acl;
418	}
419	if (aclcnt)
420		*aclcnt = entries;
421	return true;
422}
423EXPORT_SYMBOL_GPL(nfs_stream_decode_acl);