| blob | 66da8c40c559b0ae3020d063201eab02833e2681 |
1 ext4 crypto: use per-inode tfm structure
3 As suggested by Herbert Xu, we shouldn't allocate a new tfm each time
4 we read or write a page. Instead we can use a single tfm hanging off
5 the inode's crypt_info structure for all of our encryption needs for
6 that inode, since the tfm can be used by multiple crypto requests in
7 parallel.
9 Also use cmpxchg() to avoid races that could result in crypt_info
10 structure getting doubly allocated or doubly freed.
12 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
13 diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
14 index 28a0e4bd..c3a9b08 100644
15 --- a/fs/ext4/crypto.c
16 +++ b/fs/ext4/crypto.c
17 @@ -80,8 +80,6 @@ void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx)
18 ctx->w.bounce_page = NULL;
19 ctx->w.control_page = NULL;
20 if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) {
21 - if (ctx->tfm)
22 - crypto_free_tfm(ctx->tfm);
23 kmem_cache_free(ext4_crypto_ctx_cachep, ctx);
24 } else {
25 spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
26 @@ -136,36 +134,6 @@ struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode)
27 }
28 ctx->flags &= ~EXT4_WRITE_PATH_FL;
30 - /* Allocate a new Crypto API context if we don't already have
31 - * one or if it isn't the right mode. */
32 - if (ctx->tfm && (ctx->mode != ci->ci_data_mode)) {
33 - crypto_free_tfm(ctx->tfm);
34 - ctx->tfm = NULL;
35 - ctx->mode = EXT4_ENCRYPTION_MODE_INVALID;
36 - }
37 - if (!ctx->tfm) {
38 - switch (ci->ci_data_mode) {
39 - case EXT4_ENCRYPTION_MODE_AES_256_XTS:
40 - ctx->tfm = crypto_ablkcipher_tfm(
41 - crypto_alloc_ablkcipher("xts(aes)", 0, 0));
42 - break;
43 - case EXT4_ENCRYPTION_MODE_AES_256_GCM:
44 - /* TODO(mhalcrow): AEAD w/ gcm(aes);
45 - * crypto_aead_setauthsize() */
46 - ctx->tfm = ERR_PTR(-ENOTSUPP);
47 - break;
48 - default:
49 - BUG();
50 - }
51 - if (IS_ERR_OR_NULL(ctx->tfm)) {
52 - res = PTR_ERR(ctx->tfm);
53 - ctx->tfm = NULL;
54 - goto out;
55 - }
56 - ctx->mode = ci->ci_data_mode;
57 - }
58 - BUG_ON(ci->ci_size != ext4_encryption_key_size(ci->ci_data_mode));
59 -
60 out:
61 if (res) {
62 if (!IS_ERR_OR_NULL(ctx))
63 @@ -185,11 +153,8 @@ void ext4_exit_crypto(void)
64 {
65 struct ext4_crypto_ctx *pos, *n;
67 - list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list) {
68 - if (pos->tfm)
69 - crypto_free_tfm(pos->tfm);
70 + list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list)
71 kmem_cache_free(ext4_crypto_ctx_cachep, pos);
72 - }
73 INIT_LIST_HEAD(&ext4_free_crypto_ctxs);
74 if (ext4_bounce_page_pool)
75 mempool_destroy(ext4_bounce_page_pool);
76 @@ -303,32 +268,11 @@ static int ext4_page_crypto(struct ext4_crypto_ctx *ctx,
77 struct ablkcipher_request *req = NULL;
78 DECLARE_EXT4_COMPLETION_RESULT(ecr);
79 struct scatterlist dst, src;
80 - struct ext4_inode_info *ei = EXT4_I(inode);
81 - struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
82 + struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
83 + struct crypto_ablkcipher *tfm = ci->ci_ctfm;
84 int res = 0;
86 - BUG_ON(!ctx->tfm);
87 - BUG_ON(ctx->mode != ei->i_crypt_info->ci_data_mode);
88 -
89 - if (ctx->mode != EXT4_ENCRYPTION_MODE_AES_256_XTS) {
90 - printk_ratelimited(KERN_ERR
91 - "%s: unsupported crypto algorithm: %d\n",
92 - __func__, ctx->mode);
93 - return -ENOTSUPP;
94 - }
95 -
96 - crypto_ablkcipher_clear_flags(atfm, ~0);
97 - crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
98 -
99 - res = crypto_ablkcipher_setkey(atfm, ei->i_crypt_info->ci_raw,
100 - ei->i_crypt_info->ci_size);
101 - if (res) {
102 - printk_ratelimited(KERN_ERR
103 - "%s: crypto_ablkcipher_setkey() failed\n",
104 - __func__);
105 - return res;
106 - }
107 - req = ablkcipher_request_alloc(atfm, GFP_NOFS);
108 + req = ablkcipher_request_alloc(tfm, GFP_NOFS);
109 if (!req) {
110 printk_ratelimited(KERN_ERR
111 "%s: crypto_request_alloc() failed\n",
112 diff --git a/fs/ext4/crypto_fname.c b/fs/ext4/crypto_fname.c
113 index e63dd29..29a2dc9 100644
114 --- a/fs/ext4/crypto_fname.c
115 +++ b/fs/ext4/crypto_fname.c
116 @@ -252,52 +252,6 @@ static int digest_decode(const char *src, int len, char *dst)
117 return cp - dst;
118 }
120 -int ext4_setup_fname_crypto(struct inode *inode)
121 -{
122 - struct ext4_inode_info *ei = EXT4_I(inode);
123 - struct ext4_crypt_info *ci = ei->i_crypt_info;
124 - struct crypto_ablkcipher *ctfm;
125 - int res;
126 -
127 - /* Check if the crypto policy is set on the inode */
128 - res = ext4_encrypted_inode(inode);
129 - if (res == 0)
130 - return 0;
131 -
132 - res = ext4_get_encryption_info(inode);
133 - if (res < 0)
134 - return res;
135 - ci = ei->i_crypt_info;
136 -
137 - if (!ci || ci->ci_ctfm)
138 - return 0;
139 -
140 - if (ci->ci_filename_mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
141 - printk_once(KERN_WARNING "ext4: unsupported key mode %d\n",
142 - ci->ci_filename_mode);
143 - return -ENOKEY;
144 - }
145 -
146 - ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))", 0, 0);
147 - if (!ctfm || IS_ERR(ctfm)) {
148 - res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
149 - printk(KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
150 - __func__, res);
151 - return res;
152 - }
153 - crypto_ablkcipher_clear_flags(ctfm, ~0);
154 - crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
155 - CRYPTO_TFM_REQ_WEAK_KEY);
156 -
157 - res = crypto_ablkcipher_setkey(ctfm, ci->ci_raw, ci->ci_size);
158 - if (res) {
159 - crypto_free_ablkcipher(ctfm);
160 - return -EIO;
161 - }
162 - ci->ci_ctfm = ctfm;
163 - return 0;
164 -}
165 -
166 /**
167 * ext4_fname_crypto_round_up() -
168 *
169 @@ -449,7 +403,7 @@ int ext4_fname_setup_filename(struct inode *dir, const struct qstr *iname,
170 fname->disk_name.len = iname->len;
171 goto out;
172 }
173 - ret = ext4_setup_fname_crypto(dir);
174 + ret = ext4_get_encryption_info(dir);
175 if (ret)
176 return ret;
177 ci = EXT4_I(dir)->i_crypt_info;
178 diff --git a/fs/ext4/crypto_key.c b/fs/ext4/crypto_key.c
179 index 858d7d6..442d24e 100644
180 --- a/fs/ext4/crypto_key.c
181 +++ b/fs/ext4/crypto_key.c
182 @@ -84,20 +84,32 @@ out:
183 return res;
184 }
186 -void ext4_free_encryption_info(struct inode *inode)
187 +void ext4_free_crypt_info(struct ext4_crypt_info *ci)
188 {
189 - struct ext4_inode_info *ei = EXT4_I(inode);
190 - struct ext4_crypt_info *ci = ei->i_crypt_info;
191 -
192 if (!ci)
193 return;
195 if (ci->ci_keyring_key)
196 key_put(ci->ci_keyring_key);
197 crypto_free_ablkcipher(ci->ci_ctfm);
198 - memzero_explicit(&ci->ci_raw, sizeof(ci->ci_raw));
199 kmem_cache_free(ext4_crypt_info_cachep, ci);
200 - ei->i_crypt_info = NULL;
201 +}
202 +
203 +void ext4_free_encryption_info(struct inode *inode,
204 + struct ext4_crypt_info *ci)
205 +{
206 + struct ext4_inode_info *ei = EXT4_I(inode);
207 + struct ext4_crypt_info *prev;
208 +
209 + if (ci == NULL)
210 + ci = ACCESS_ONCE(ei->i_crypt_info);
211 + if (ci == NULL)
212 + return;
213 + prev = cmpxchg(&ei->i_crypt_info, ci, NULL);
214 + if (prev != ci)
215 + return;
216 +
217 + ext4_free_crypt_info(ci);
218 }
220 int _ext4_get_encryption_info(struct inode *inode)
221 @@ -111,6 +123,10 @@ int _ext4_get_encryption_info(struct inode *inode)
222 struct ext4_encryption_context ctx;
223 struct user_key_payload *ukp;
224 struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
225 + struct crypto_ablkcipher *ctfm;
226 + const char *cipher_str;
227 + char raw_key[EXT4_MAX_KEY_SIZE];
228 + char mode;
229 int res;
231 if (!ext4_read_workqueue) {
232 @@ -119,11 +135,14 @@ int _ext4_get_encryption_info(struct inode *inode)
233 return res;
234 }
236 - if (ei->i_crypt_info) {
237 - if (!ei->i_crypt_info->ci_keyring_key ||
238 - key_validate(ei->i_crypt_info->ci_keyring_key) == 0)
239 +retry:
240 + crypt_info = ACCESS_ONCE(ei->i_crypt_info);
241 + if (crypt_info) {
242 + if (!crypt_info->ci_keyring_key ||
243 + key_validate(crypt_info->ci_keyring_key) == 0)
244 return 0;
245 - ext4_free_encryption_info(inode);
246 + ext4_free_encryption_info(inode, crypt_info);
247 + goto retry;
248 }
250 res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
251 @@ -144,26 +163,37 @@ int _ext4_get_encryption_info(struct inode *inode)
252 if (!crypt_info)
253 return -ENOMEM;
255 - ei->i_crypt_policy_flags = ctx.flags;
256 crypt_info->ci_flags = ctx.flags;
257 crypt_info->ci_data_mode = ctx.contents_encryption_mode;
258 crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
259 crypt_info->ci_ctfm = NULL;
260 + crypt_info->ci_keyring_key = NULL;
261 memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
262 sizeof(crypt_info->ci_master_key));
263 if (S_ISREG(inode->i_mode))
264 - crypt_info->ci_size =
265 - ext4_encryption_key_size(crypt_info->ci_data_mode);
266 + mode = crypt_info->ci_data_mode;
267 else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
268 - crypt_info->ci_size =
269 - ext4_encryption_key_size(crypt_info->ci_filename_mode);
270 + mode = crypt_info->ci_filename_mode;
271 else
272 BUG();
273 - BUG_ON(!crypt_info->ci_size);
274 - if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
275 - memset(crypt_info->ci_raw, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
276 + switch (mode) {
277 + case EXT4_ENCRYPTION_MODE_AES_256_XTS:
278 + cipher_str = "xts(aes)";
279 + break;
280 + case EXT4_ENCRYPTION_MODE_AES_256_CTS:
281 + cipher_str = "cts(cbc(aes))";
282 + break;
283 + default:
284 + printk_once(KERN_WARNING
285 + "ext4: unsupported key mode %d (ino %u)\n",
286 + mode, (unsigned) inode->i_ino);
287 + res = -ENOKEY;
288 goto out;
289 }
290 + if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
291 + memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
292 + goto got_key;
293 + }
294 memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
295 EXT4_KEY_DESC_PREFIX_SIZE);
296 sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
297 @@ -177,6 +207,7 @@ int _ext4_get_encryption_info(struct inode *inode)
298 keyring_key = NULL;
299 goto out;
300 }
301 + crypt_info->ci_keyring_key = keyring_key;
302 BUG_ON(keyring_key->type != &key_type_logon);
303 ukp = ((struct user_key_payload *)keyring_key->payload.data);
304 if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
305 @@ -188,19 +219,36 @@ int _ext4_get_encryption_info(struct inode *inode)
306 EXT4_KEY_DERIVATION_NONCE_SIZE);
307 BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE);
308 res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
309 - crypt_info->ci_raw);
310 -out:
311 - if (res < 0) {
312 - if (res == -ENOKEY)
313 - res = 0;
314 - kmem_cache_free(ext4_crypt_info_cachep, crypt_info);
315 - } else {
316 - ei->i_crypt_info = crypt_info;
317 - crypt_info->ci_keyring_key = keyring_key;
318 - keyring_key = NULL;
319 + raw_key);
320 +got_key:
321 + ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
322 + if (!ctfm || IS_ERR(ctfm)) {
323 + res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
324 + printk(KERN_DEBUG
325 + "%s: error %d (inode %u) allocating crypto tfm\n",
326 + __func__, res, (unsigned) inode->i_ino);
327 + goto out;
328 + }
329 + crypt_info->ci_ctfm = ctfm;
330 + crypto_ablkcipher_clear_flags(ctfm, ~0);
331 + crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
332 + CRYPTO_TFM_REQ_WEAK_KEY);
333 + res = crypto_ablkcipher_setkey(ctfm, raw_key,
334 + ext4_encryption_key_size(mode));
335 + if (res)
336 + goto out;
337 + memzero_explicit(raw_key, sizeof(raw_key));
338 + if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
339 + ext4_free_crypt_info(crypt_info);
340 + goto retry;
341 }
342 - if (keyring_key)
343 - key_put(keyring_key);
344 + return 0;
345 +
346 +out:
347 + if (res == -ENOKEY)
348 + res = 0;
349 + ext4_free_crypt_info(crypt_info);
350 + memzero_explicit(raw_key, sizeof(raw_key));
351 return res;
352 }
354 diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
355 index 28cb94f..e11e6ae 100644
356 --- a/fs/ext4/dir.c
357 +++ b/fs/ext4/dir.c
358 @@ -133,9 +133,6 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
359 return err;
360 }
362 - err = ext4_setup_fname_crypto(inode);
363 - if (err)
364 - return err;
365 if (ext4_encrypted_inode(inode)) {
366 err = ext4_fname_crypto_alloc_buffer(inode, EXT4_NAME_LEN,
367 &fname_crypto_str);
368 diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
369 index 23e33fb..7435ff2 100644
370 --- a/fs/ext4/ext4.h
371 +++ b/fs/ext4/ext4.h
372 @@ -911,7 +911,6 @@ struct ext4_inode_info {
374 /* on-disk additional length */
375 __u16 i_extra_isize;
376 - char i_crypt_policy_flags;
378 /* Indicate the inline data space. */
379 u16 i_inline_off;
380 @@ -2105,7 +2104,6 @@ int ext4_fname_usr_to_disk(struct inode *inode,
381 const struct qstr *iname,
382 struct ext4_str *oname);
383 #ifdef CONFIG_EXT4_FS_ENCRYPTION
384 -int ext4_setup_fname_crypto(struct inode *inode);
385 void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str);
386 int ext4_fname_setup_filename(struct inode *dir, const struct qstr *iname,
387 int lookup, struct ext4_filename *fname);
388 @@ -2131,7 +2129,8 @@ static inline void ext4_fname_free_filename(struct ext4_filename *fname) { }
391 /* crypto_key.c */
392 -void ext4_free_encryption_info(struct inode *inode);
393 +void ext4_free_crypt_info(struct ext4_crypt_info *ci);
394 +void ext4_free_encryption_info(struct inode *inode, struct ext4_crypt_info *ci);
395 int _ext4_get_encryption_info(struct inode *inode);
397 #ifdef CONFIG_EXT4_FS_ENCRYPTION
398 diff --git a/fs/ext4/ext4_crypto.h b/fs/ext4/ext4_crypto.h
399 index c5258f2..34e0d24 100644
400 --- a/fs/ext4/ext4_crypto.h
401 +++ b/fs/ext4/ext4_crypto.h
402 @@ -74,13 +74,11 @@ struct ext4_encryption_key {
403 } __attribute__((__packed__));
405 struct ext4_crypt_info {
406 - unsigned char ci_size;
407 char ci_data_mode;
408 char ci_filename_mode;
409 char ci_flags;
410 struct crypto_ablkcipher *ci_ctfm;
411 struct key *ci_keyring_key;
412 - char ci_raw[EXT4_MAX_KEY_SIZE];
413 char ci_master_key[EXT4_KEY_DESCRIPTOR_SIZE];
414 };
416 @@ -89,7 +87,6 @@ struct ext4_crypt_info {
417 #define EXT4_WRITE_PATH_FL 0x00000004
419 struct ext4_crypto_ctx {
420 - struct crypto_tfm *tfm; /* Crypto API context */
421 union {
422 struct {
423 struct page *bounce_page; /* Ciphertext page */
424 diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
425 index 9bed99f..6ab50f8 100644
426 --- a/fs/ext4/namei.c
427 +++ b/fs/ext4/namei.c
428 @@ -607,11 +607,12 @@ static struct stats dx_show_leaf(struct inode *dir,
429 char *name;
430 struct ext4_str fname_crypto_str
431 = {.name = NULL, .len = 0};
432 - int res;
433 + int res = 0;
435 name = de->name;
436 len = de->name_len;
437 - res = ext4_setup_fname_crypto(dir);
438 + if (ext4_encrypted_inode(inode))
439 + res = ext4_get_encryption_info(dir);
440 if (res) {
441 printk(KERN_WARNING "Error setting up"
442 " fname crypto: %d\n", res);
443 @@ -953,12 +954,12 @@ static int htree_dirblock_to_tree(struct file *dir_file,
444 EXT4_DIR_REC_LEN(0));
445 #ifdef CONFIG_EXT4_FS_ENCRYPTION
446 /* Check if the directory is encrypted */
447 - err = ext4_setup_fname_crypto(dir);
448 - if (err) {
449 - brelse(bh);
450 - return err;
451 - }
452 if (ext4_encrypted_inode(dir)) {
453 + err = ext4_get_encryption_info(dir);
454 + if (err < 0) {
455 + brelse(bh);
456 + return err;
457 + }
458 err = ext4_fname_crypto_alloc_buffer(dir, EXT4_NAME_LEN,
459 &fname_crypto_str);
460 if (err < 0) {
461 @@ -3108,7 +3109,7 @@ static int ext4_symlink(struct inode *dir,
462 err = ext4_inherit_context(dir, inode);
463 if (err)
464 goto err_drop_inode;
465 - err = ext4_setup_fname_crypto(inode);
466 + err = ext4_get_encryption_info(inode);
467 if (err)
468 goto err_drop_inode;
469 istr.name = (const unsigned char *) symname;
470 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
471 index b0bd1c1..56bfc2f 100644
472 --- a/fs/ext4/super.c
473 +++ b/fs/ext4/super.c
474 @@ -959,7 +959,7 @@ void ext4_clear_inode(struct inode *inode)
475 }
476 #ifdef CONFIG_EXT4_FS_ENCRYPTION
477 if (EXT4_I(inode)->i_crypt_info)
478 - ext4_free_encryption_info(inode);
479 + ext4_free_encryption_info(inode, EXT4_I(inode)->i_crypt_info);
480 #endif
481 }
483 diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
484 index 3287088..68e915a 100644
485 --- a/fs/ext4/symlink.c
486 +++ b/fs/ext4/symlink.c
487 @@ -37,7 +37,7 @@ static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd)
488 if (!ext4_encrypted_inode(inode))
489 return page_follow_link_light(dentry, nd);
491 - res = ext4_setup_fname_crypto(inode);
492 + res = ext4_get_encryption_info(inode);
493 if (res)
494 return ERR_PTR(res);