cifs: fix writeback race with file that is growing
[linux-3.10.git] / fs / cifs / smb2transport.c
1 /*
2  *   fs/cifs/smb2transport.c
3  *
4  *   Copyright (C) International Business Machines  Corp., 2002, 2011
5  *                 Etersoft, 2012
6  *   Author(s): Steve French (sfrench@us.ibm.com)
7  *              Jeremy Allison (jra@samba.org) 2006
8  *              Pavel Shilovsky (pshilovsky@samba.org) 2012
9  *
10  *   This library is free software; you can redistribute it and/or modify
11  *   it under the terms of the GNU Lesser General Public License as published
12  *   by the Free Software Foundation; either version 2.1 of the License, or
13  *   (at your option) any later version.
14  *
15  *   This library is distributed in the hope that it will be useful,
16  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
17  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
18  *   the GNU Lesser General Public License for more details.
19  *
20  *   You should have received a copy of the GNU Lesser General Public License
21  *   along with this library; if not, write to the Free Software
22  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23  */
24
25 #include <linux/fs.h>
26 #include <linux/list.h>
27 #include <linux/wait.h>
28 #include <linux/net.h>
29 #include <linux/delay.h>
30 #include <linux/uaccess.h>
31 #include <asm/processor.h>
32 #include <linux/mempool.h>
33 #include <linux/highmem.h>
34 #include "smb2pdu.h"
35 #include "cifsglob.h"
36 #include "cifsproto.h"
37 #include "smb2proto.h"
38 #include "cifs_debug.h"
39 #include "smb2status.h"
40 #include "smb2glob.h"
41
42 static int
43 smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
44 {
45         int i, rc;
46         unsigned char smb2_signature[SMB2_HMACSHA256_SIZE];
47         unsigned char *sigptr = smb2_signature;
48         struct kvec *iov = rqst->rq_iov;
49         int n_vec = rqst->rq_nvec;
50         struct smb2_hdr *smb2_pdu = (struct smb2_hdr *)iov[0].iov_base;
51
52         memset(smb2_signature, 0x0, SMB2_HMACSHA256_SIZE);
53         memset(smb2_pdu->Signature, 0x0, SMB2_SIGNATURE_SIZE);
54
55         rc = crypto_shash_setkey(server->secmech.hmacsha256,
56                 server->session_key.response, SMB2_NTLMV2_SESSKEY_SIZE);
57         if (rc) {
58                 cERROR(1, "%s: Could not update with response\n", __func__);
59                 return rc;
60         }
61
62         rc = crypto_shash_init(&server->secmech.sdeschmacsha256->shash);
63         if (rc) {
64                 cERROR(1, "%s: Could not init md5\n", __func__);
65                 return rc;
66         }
67
68         for (i = 0; i < n_vec; i++) {
69                 if (iov[i].iov_len == 0)
70                         continue;
71                 if (iov[i].iov_base == NULL) {
72                         cERROR(1, "null iovec entry");
73                         return -EIO;
74                 }
75                 /*
76                  * The first entry includes a length field (which does not get
77                  * signed that occupies the first 4 bytes before the header).
78                  */
79                 if (i == 0) {
80                         if (iov[0].iov_len <= 8) /* cmd field at offset 9 */
81                                 break; /* nothing to sign or corrupt header */
82                         rc =
83                         crypto_shash_update(
84                                 &server->secmech.sdeschmacsha256->shash,
85                                 iov[i].iov_base + 4, iov[i].iov_len - 4);
86                 } else {
87                         rc =
88                         crypto_shash_update(
89                                 &server->secmech.sdeschmacsha256->shash,
90                                 iov[i].iov_base, iov[i].iov_len);
91                 }
92                 if (rc) {
93                         cERROR(1, "%s: Could not update with payload\n",
94                                                         __func__);
95                         return rc;
96                 }
97         }
98
99         /* now hash over the rq_pages array */
100         for (i = 0; i < rqst->rq_npages; i++) {
101                 struct kvec p_iov;
102
103                 cifs_rqst_page_to_kvec(rqst, i, &p_iov);
104                 crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
105                                         p_iov.iov_base, p_iov.iov_len);
106                 kunmap(rqst->rq_pages[i]);
107         }
108
109         rc = crypto_shash_final(&server->secmech.sdeschmacsha256->shash,
110                                 sigptr);
111         if (rc)
112                 cERROR(1, "%s: Could not generate sha256 hash\n", __func__);
113
114         memcpy(smb2_pdu->Signature, sigptr, SMB2_SIGNATURE_SIZE);
115
116         return rc;
117 }
118
119 /* must be called with server->srv_mutex held */
120 static int
121 smb2_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server)
122 {
123         int rc = 0;
124         struct smb2_hdr *smb2_pdu = rqst->rq_iov[0].iov_base;
125
126         if (!(smb2_pdu->Flags & SMB2_FLAGS_SIGNED) ||
127             server->tcpStatus == CifsNeedNegotiate)
128                 return rc;
129
130         if (!server->session_estab) {
131                 strncpy(smb2_pdu->Signature, "BSRSPYL", 8);
132                 return rc;
133         }
134
135         rc = smb2_calc_signature(rqst, server);
136
137         return rc;
138 }
139
140 int
141 smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
142 {
143         unsigned int rc;
144         char server_response_sig[16];
145         struct smb2_hdr *smb2_pdu = (struct smb2_hdr *)rqst->rq_iov[0].iov_base;
146
147         if ((smb2_pdu->Command == SMB2_NEGOTIATE) ||
148             (smb2_pdu->Command == SMB2_OPLOCK_BREAK) ||
149             (!server->session_estab))
150                 return 0;
151
152         /*
153          * BB what if signatures are supposed to be on for session but
154          * server does not send one? BB
155          */
156
157         /* Do not need to verify session setups with signature "BSRSPYL " */
158         if (memcmp(smb2_pdu->Signature, "BSRSPYL ", 8) == 0)
159                 cFYI(1, "dummy signature received for smb command 0x%x",
160                         smb2_pdu->Command);
161
162         /*
163          * Save off the origiginal signature so we can modify the smb and check
164          * our calculated signature against what the server sent.
165          */
166         memcpy(server_response_sig, smb2_pdu->Signature, SMB2_SIGNATURE_SIZE);
167
168         memset(smb2_pdu->Signature, 0, SMB2_SIGNATURE_SIZE);
169
170         mutex_lock(&server->srv_mutex);
171         rc = smb2_calc_signature(rqst, server);
172         mutex_unlock(&server->srv_mutex);
173
174         if (rc)
175                 return rc;
176
177         if (memcmp(server_response_sig, smb2_pdu->Signature,
178                    SMB2_SIGNATURE_SIZE))
179                 return -EACCES;
180         else
181                 return 0;
182 }
183
184 /*
185  * Set message id for the request. Should be called after wait_for_free_request
186  * and when srv_mutex is held.
187  */
188 static inline void
189 smb2_seq_num_into_buf(struct TCP_Server_Info *server, struct smb2_hdr *hdr)
190 {
191         hdr->MessageId = get_next_mid(server);
192 }
193
194 static struct mid_q_entry *
195 smb2_mid_entry_alloc(const struct smb2_hdr *smb_buffer,
196                      struct TCP_Server_Info *server)
197 {
198         struct mid_q_entry *temp;
199
200         if (server == NULL) {
201                 cERROR(1, "Null TCP session in smb2_mid_entry_alloc");
202                 return NULL;
203         }
204
205         temp = mempool_alloc(cifs_mid_poolp, GFP_NOFS);
206         if (temp == NULL)
207                 return temp;
208         else {
209                 memset(temp, 0, sizeof(struct mid_q_entry));
210                 temp->mid = smb_buffer->MessageId;      /* always LE */
211                 temp->pid = current->pid;
212                 temp->command = smb_buffer->Command;    /* Always LE */
213                 temp->when_alloc = jiffies;
214                 temp->server = server;
215
216                 /*
217                  * The default is for the mid to be synchronous, so the
218                  * default callback just wakes up the current task.
219                  */
220                 temp->callback = cifs_wake_up_task;
221                 temp->callback_data = current;
222         }
223
224         atomic_inc(&midCount);
225         temp->mid_state = MID_REQUEST_ALLOCATED;
226         return temp;
227 }
228
229 static int
230 smb2_get_mid_entry(struct cifs_ses *ses, struct smb2_hdr *buf,
231                    struct mid_q_entry **mid)
232 {
233         if (ses->server->tcpStatus == CifsExiting)
234                 return -ENOENT;
235
236         if (ses->server->tcpStatus == CifsNeedReconnect) {
237                 cFYI(1, "tcp session dead - return to caller to retry");
238                 return -EAGAIN;
239         }
240
241         if (ses->status != CifsGood) {
242                 /* check if SMB2 session is bad because we are setting it up */
243                 if ((buf->Command != SMB2_SESSION_SETUP) &&
244                     (buf->Command != SMB2_NEGOTIATE))
245                         return -EAGAIN;
246                 /* else ok - we are setting up session */
247         }
248         *mid = smb2_mid_entry_alloc(buf, ses->server);
249         if (*mid == NULL)
250                 return -ENOMEM;
251         spin_lock(&GlobalMid_Lock);
252         list_add_tail(&(*mid)->qhead, &ses->server->pending_mid_q);
253         spin_unlock(&GlobalMid_Lock);
254         return 0;
255 }
256
257 int
258 smb2_check_receive(struct mid_q_entry *mid, struct TCP_Server_Info *server,
259                    bool log_error)
260 {
261         unsigned int len = get_rfc1002_length(mid->resp_buf);
262         struct kvec iov;
263         struct smb_rqst rqst = { .rq_iov = &iov,
264                                  .rq_nvec = 1 };
265
266         iov.iov_base = (char *)mid->resp_buf;
267         iov.iov_len = get_rfc1002_length(mid->resp_buf) + 4;
268
269         dump_smb(mid->resp_buf, min_t(u32, 80, len));
270         /* convert the length into a more usable form */
271         if ((len > 24) &&
272             (server->sec_mode & (SECMODE_SIGN_REQUIRED|SECMODE_SIGN_ENABLED))) {
273                 int rc;
274
275                 rc = smb2_verify_signature(&rqst, server);
276                 if (rc)
277                         cERROR(1, "SMB signature verification returned error = "
278                                "%d", rc);
279         }
280
281         return map_smb2_to_linux_error(mid->resp_buf, log_error);
282 }
283
284 struct mid_q_entry *
285 smb2_setup_request(struct cifs_ses *ses, struct smb_rqst *rqst)
286 {
287         int rc;
288         struct smb2_hdr *hdr = (struct smb2_hdr *)rqst->rq_iov[0].iov_base;
289         struct mid_q_entry *mid;
290
291         smb2_seq_num_into_buf(ses->server, hdr);
292
293         rc = smb2_get_mid_entry(ses, hdr, &mid);
294         if (rc)
295                 return ERR_PTR(rc);
296         rc = smb2_sign_rqst(rqst, ses->server);
297         if (rc) {
298                 cifs_delete_mid(mid);
299                 return ERR_PTR(rc);
300         }
301         return mid;
302 }
303
304 struct mid_q_entry *
305 smb2_setup_async_request(struct TCP_Server_Info *server, struct smb_rqst *rqst)
306 {
307         int rc;
308         struct smb2_hdr *hdr = (struct smb2_hdr *)rqst->rq_iov[0].iov_base;
309         struct mid_q_entry *mid;
310
311         smb2_seq_num_into_buf(server, hdr);
312
313         mid = smb2_mid_entry_alloc(hdr, server);
314         if (mid == NULL)
315                 return ERR_PTR(-ENOMEM);
316
317         rc = smb2_sign_rqst(rqst, server);
318         if (rc) {
319                 DeleteMidQEntry(mid);
320                 return ERR_PTR(rc);
321         }
322
323         return mid;
324 }