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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Data verification functions, i.e. hooks for ->readahead()
4 *
5 * Copyright 2019 Google LLC
6 */
7
8#include "fsverity_private.h"
9
10#include <crypto/hash.h>
11#include <linux/bio.h>
12
13static struct workqueue_struct *fsverity_read_workqueue;
14
15/*
16 * Returns true if the hash block with index @hblock_idx in the tree, located in
17 * @hpage, has already been verified.
18 */
19static bool is_hash_block_verified(struct fsverity_info *vi, struct page *hpage,
20 unsigned long hblock_idx)
21{
22 bool verified;
23 unsigned int blocks_per_page;
24 unsigned int i;
25
26 /*
27 * When the Merkle tree block size and page size are the same, then the
28 * ->hash_block_verified bitmap isn't allocated, and we use PG_checked
29 * to directly indicate whether the page's block has been verified.
30 *
31 * Using PG_checked also guarantees that we re-verify hash pages that
32 * get evicted and re-instantiated from the backing storage, as new
33 * pages always start out with PG_checked cleared.
34 */
35 if (!vi->hash_block_verified)
36 return PageChecked(hpage);
37
38 /*
39 * When the Merkle tree block size and page size differ, we use a bitmap
40 * to indicate whether each hash block has been verified.
41 *
42 * However, we still need to ensure that hash pages that get evicted and
43 * re-instantiated from the backing storage are re-verified. To do
44 * this, we use PG_checked again, but now it doesn't really mean
45 * "checked". Instead, now it just serves as an indicator for whether
46 * the hash page is newly instantiated or not.
47 *
48 * The first thread that sees PG_checked=0 must clear the corresponding
49 * bitmap bits, then set PG_checked=1. This requires a spinlock. To
50 * avoid having to take this spinlock in the common case of
51 * PG_checked=1, we start with an opportunistic lockless read.
52 */
53 if (PageChecked(hpage)) {
54 /*
55 * A read memory barrier is needed here to give ACQUIRE
56 * semantics to the above PageChecked() test.
57 */
58 smp_rmb();
59 return test_bit(hblock_idx, vi->hash_block_verified);
60 }
61 spin_lock(&vi->hash_page_init_lock);
62 if (PageChecked(hpage)) {
63 verified = test_bit(hblock_idx, vi->hash_block_verified);
64 } else {
65 blocks_per_page = vi->tree_params.blocks_per_page;
66 hblock_idx = round_down(hblock_idx, blocks_per_page);
67 for (i = 0; i < blocks_per_page; i++)
68 clear_bit(hblock_idx + i, vi->hash_block_verified);
69 /*
70 * A write memory barrier is needed here to give RELEASE
71 * semantics to the below SetPageChecked() operation.
72 */
73 smp_wmb();
74 SetPageChecked(hpage);
75 verified = false;
76 }
77 spin_unlock(&vi->hash_page_init_lock);
78 return verified;
79}
80
81/*
82 * Verify a single data block against the file's Merkle tree.
83 *
84 * In principle, we need to verify the entire path to the root node. However,
85 * for efficiency the filesystem may cache the hash blocks. Therefore we need
86 * only ascend the tree until an already-verified hash block is seen, and then
87 * verify the path to that block.
88 *
89 * Return: %true if the data block is valid, else %false.
90 */
91static bool
92verify_data_block(struct inode *inode, struct fsverity_info *vi,
93 const void *data, u64 data_pos, unsigned long max_ra_pages)
94{
95 const struct merkle_tree_params *params = &vi->tree_params;
96 const unsigned int hsize = params->digest_size;
97 int level;
98 u8 _want_hash[FS_VERITY_MAX_DIGEST_SIZE];
99 const u8 *want_hash;
100 u8 real_hash[FS_VERITY_MAX_DIGEST_SIZE];
101 /* The hash blocks that are traversed, indexed by level */
102 struct {
103 /* Page containing the hash block */
104 struct page *page;
105 /* Mapped address of the hash block (will be within @page) */
106 const void *addr;
107 /* Index of the hash block in the tree overall */
108 unsigned long index;
109 /* Byte offset of the wanted hash relative to @addr */
110 unsigned int hoffset;
111 } hblocks[FS_VERITY_MAX_LEVELS];
112 /*
113 * The index of the previous level's block within that level; also the
114 * index of that block's hash within the current level.
115 */
116 u64 hidx = data_pos >> params->log_blocksize;
117
118 /* Up to 1 + FS_VERITY_MAX_LEVELS pages may be mapped at once */
119 BUILD_BUG_ON(1 + FS_VERITY_MAX_LEVELS > KM_MAX_IDX);
120
121 if (unlikely(data_pos >= inode->i_size)) {
122 /*
123 * This can happen in the data page spanning EOF when the Merkle
124 * tree block size is less than the page size. The Merkle tree
125 * doesn't cover data blocks fully past EOF. But the entire
126 * page spanning EOF can be visible to userspace via a mmap, and
127 * any part past EOF should be all zeroes. Therefore, we need
128 * to verify that any data blocks fully past EOF are all zeroes.
129 */
130 if (memchr_inv(data, 0, params->block_size)) {
131 fsverity_err(inode,
132 "FILE CORRUPTED! Data past EOF is not zeroed");
133 return false;
134 }
135 return true;
136 }
137
138 /*
139 * Starting at the leaf level, ascend the tree saving hash blocks along
140 * the way until we find a hash block that has already been verified, or
141 * until we reach the root.
142 */
143 for (level = 0; level < params->num_levels; level++) {
144 unsigned long next_hidx;
145 unsigned long hblock_idx;
146 pgoff_t hpage_idx;
147 unsigned int hblock_offset_in_page;
148 unsigned int hoffset;
149 struct page *hpage;
150 const void *haddr;
151
152 /*
153 * The index of the block in the current level; also the index
154 * of that block's hash within the next level.
155 */
156 next_hidx = hidx >> params->log_arity;
157
158 /* Index of the hash block in the tree overall */
159 hblock_idx = params->level_start[level] + next_hidx;
160
161 /* Index of the hash page in the tree overall */
162 hpage_idx = hblock_idx >> params->log_blocks_per_page;
163
164 /* Byte offset of the hash block within the page */
165 hblock_offset_in_page =
166 (hblock_idx << params->log_blocksize) & ~PAGE_MASK;
167
168 /* Byte offset of the hash within the block */
169 hoffset = (hidx << params->log_digestsize) &
170 (params->block_size - 1);
171
172 hpage = inode->i_sb->s_vop->read_merkle_tree_page(inode,
173 hpage_idx, level == 0 ? min(max_ra_pages,
174 params->tree_pages - hpage_idx) : 0);
175 if (IS_ERR(hpage)) {
176 fsverity_err(inode,
177 "Error %ld reading Merkle tree page %lu",
178 PTR_ERR(hpage), hpage_idx);
179 goto error;
180 }
181 haddr = kmap_local_page(hpage) + hblock_offset_in_page;
182 if (is_hash_block_verified(vi, hpage, hblock_idx)) {
183 memcpy(_want_hash, haddr + hoffset, hsize);
184 want_hash = _want_hash;
185 kunmap_local(haddr);
186 put_page(hpage);
187 goto descend;
188 }
189 hblocks[level].page = hpage;
190 hblocks[level].addr = haddr;
191 hblocks[level].index = hblock_idx;
192 hblocks[level].hoffset = hoffset;
193 hidx = next_hidx;
194 }
195
196 want_hash = vi->root_hash;
197descend:
198 /* Descend the tree verifying hash blocks. */
199 for (; level > 0; level--) {
200 struct page *hpage = hblocks[level - 1].page;
201 const void *haddr = hblocks[level - 1].addr;
202 unsigned long hblock_idx = hblocks[level - 1].index;
203 unsigned int hoffset = hblocks[level - 1].hoffset;
204
205 if (fsverity_hash_block(params, inode, haddr, real_hash) != 0)
206 goto error;
207 if (memcmp(want_hash, real_hash, hsize) != 0)
208 goto corrupted;
209 /*
210 * Mark the hash block as verified. This must be atomic and
211 * idempotent, as the same hash block might be verified by
212 * multiple threads concurrently.
213 */
214 if (vi->hash_block_verified)
215 set_bit(hblock_idx, vi->hash_block_verified);
216 else
217 SetPageChecked(hpage);
218 memcpy(_want_hash, haddr + hoffset, hsize);
219 want_hash = _want_hash;
220 kunmap_local(haddr);
221 put_page(hpage);
222 }
223
224 /* Finally, verify the data block. */
225 if (fsverity_hash_block(params, inode, data, real_hash) != 0)
226 goto error;
227 if (memcmp(want_hash, real_hash, hsize) != 0)
228 goto corrupted;
229 return true;
230
231corrupted:
232 fsverity_err(inode,
233 "FILE CORRUPTED! pos=%llu, level=%d, want_hash=%s:%*phN, real_hash=%s:%*phN",
234 data_pos, level - 1,
235 params->hash_alg->name, hsize, want_hash,
236 params->hash_alg->name, hsize, real_hash);
237error:
238 for (; level > 0; level--) {
239 kunmap_local(hblocks[level - 1].addr);
240 put_page(hblocks[level - 1].page);
241 }
242 return false;
243}
244
245static bool
246verify_data_blocks(struct folio *data_folio, size_t len, size_t offset,
247 unsigned long max_ra_pages)
248{
249 struct inode *inode = data_folio->mapping->host;
250 struct fsverity_info *vi = inode->i_verity_info;
251 const unsigned int block_size = vi->tree_params.block_size;
252 u64 pos = (u64)data_folio->index << PAGE_SHIFT;
253
254 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offset, block_size)))
255 return false;
256 if (WARN_ON_ONCE(!folio_test_locked(data_folio) ||
257 folio_test_uptodate(data_folio)))
258 return false;
259 do {
260 void *data;
261 bool valid;
262
263 data = kmap_local_folio(data_folio, offset);
264 valid = verify_data_block(inode, vi, data, pos + offset,
265 max_ra_pages);
266 kunmap_local(data);
267 if (!valid)
268 return false;
269 offset += block_size;
270 len -= block_size;
271 } while (len);
272 return true;
273}
274
275/**
276 * fsverity_verify_blocks() - verify data in a folio
277 * @folio: the folio containing the data to verify
278 * @len: the length of the data to verify in the folio
279 * @offset: the offset of the data to verify in the folio
280 *
281 * Verify data that has just been read from a verity file. The data must be
282 * located in a pagecache folio that is still locked and not yet uptodate. The
283 * length and offset of the data must be Merkle tree block size aligned.
284 *
285 * Return: %true if the data is valid, else %false.
286 */
287bool fsverity_verify_blocks(struct folio *folio, size_t len, size_t offset)
288{
289 return verify_data_blocks(folio, len, offset, 0);
290}
291EXPORT_SYMBOL_GPL(fsverity_verify_blocks);
292
293#ifdef CONFIG_BLOCK
294/**
295 * fsverity_verify_bio() - verify a 'read' bio that has just completed
296 * @bio: the bio to verify
297 *
298 * Verify the bio's data against the file's Merkle tree. All bio data segments
299 * must be aligned to the file's Merkle tree block size. If any data fails
300 * verification, then bio->bi_status is set to an error status.
301 *
302 * This is a helper function for use by the ->readahead() method of filesystems
303 * that issue bios to read data directly into the page cache. Filesystems that
304 * populate the page cache without issuing bios (e.g. non block-based
305 * filesystems) must instead call fsverity_verify_page() directly on each page.
306 * All filesystems must also call fsverity_verify_page() on holes.
307 */
308void fsverity_verify_bio(struct bio *bio)
309{
310 struct folio_iter fi;
311 unsigned long max_ra_pages = 0;
312
313 if (bio->bi_opf & REQ_RAHEAD) {
314 /*
315 * If this bio is for data readahead, then we also do readahead
316 * of the first (largest) level of the Merkle tree. Namely,
317 * when a Merkle tree page is read, we also try to piggy-back on
318 * some additional pages -- up to 1/4 the number of data pages.
319 *
320 * This improves sequential read performance, as it greatly
321 * reduces the number of I/O requests made to the Merkle tree.
322 */
323 max_ra_pages = bio->bi_iter.bi_size >> (PAGE_SHIFT + 2);
324 }
325
326 bio_for_each_folio_all(fi, bio) {
327 if (!verify_data_blocks(fi.folio, fi.length, fi.offset,
328 max_ra_pages)) {
329 bio->bi_status = BLK_STS_IOERR;
330 break;
331 }
332 }
333}
334EXPORT_SYMBOL_GPL(fsverity_verify_bio);
335#endif /* CONFIG_BLOCK */
336
337/**
338 * fsverity_enqueue_verify_work() - enqueue work on the fs-verity workqueue
339 * @work: the work to enqueue
340 *
341 * Enqueue verification work for asynchronous processing.
342 */
343void fsverity_enqueue_verify_work(struct work_struct *work)
344{
345 queue_work(fsverity_read_workqueue, work);
346}
347EXPORT_SYMBOL_GPL(fsverity_enqueue_verify_work);
348
349void __init fsverity_init_workqueue(void)
350{
351 /*
352 * Use a high-priority workqueue to prioritize verification work, which
353 * blocks reads from completing, over regular application tasks.
354 *
355 * For performance reasons, don't use an unbound workqueue. Using an
356 * unbound workqueue for crypto operations causes excessive scheduler
357 * latency on ARM64.
358 */
359 fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue",
360 WQ_HIGHPRI,
361 num_online_cpus());
362 if (!fsverity_read_workqueue)
363 panic("failed to allocate fsverity_read_queue");
364}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Data verification functions, i.e. hooks for ->readpages()
4 *
5 * Copyright 2019 Google LLC
6 */
7
8#include "fsverity_private.h"
9
10#include <crypto/hash.h>
11#include <linux/bio.h>
12#include <linux/ratelimit.h>
13
14static struct workqueue_struct *fsverity_read_workqueue;
15
16/**
17 * hash_at_level() - compute the location of the block's hash at the given level
18 *
19 * @params: (in) the Merkle tree parameters
20 * @dindex: (in) the index of the data block being verified
21 * @level: (in) the level of hash we want (0 is leaf level)
22 * @hindex: (out) the index of the hash block containing the wanted hash
23 * @hoffset: (out) the byte offset to the wanted hash within the hash block
24 */
25static void hash_at_level(const struct merkle_tree_params *params,
26 pgoff_t dindex, unsigned int level, pgoff_t *hindex,
27 unsigned int *hoffset)
28{
29 pgoff_t position;
30
31 /* Offset of the hash within the level's region, in hashes */
32 position = dindex >> (level * params->log_arity);
33
34 /* Index of the hash block in the tree overall */
35 *hindex = params->level_start[level] + (position >> params->log_arity);
36
37 /* Offset of the wanted hash (in bytes) within the hash block */
38 *hoffset = (position & ((1 << params->log_arity) - 1)) <<
39 (params->log_blocksize - params->log_arity);
40}
41
42/* Extract a hash from a hash page */
43static void extract_hash(struct page *hpage, unsigned int hoffset,
44 unsigned int hsize, u8 *out)
45{
46 void *virt = kmap_atomic(hpage);
47
48 memcpy(out, virt + hoffset, hsize);
49 kunmap_atomic(virt);
50}
51
52static inline int cmp_hashes(const struct fsverity_info *vi,
53 const u8 *want_hash, const u8 *real_hash,
54 pgoff_t index, int level)
55{
56 const unsigned int hsize = vi->tree_params.digest_size;
57
58 if (memcmp(want_hash, real_hash, hsize) == 0)
59 return 0;
60
61 fsverity_err(vi->inode,
62 "FILE CORRUPTED! index=%lu, level=%d, want_hash=%s:%*phN, real_hash=%s:%*phN",
63 index, level,
64 vi->tree_params.hash_alg->name, hsize, want_hash,
65 vi->tree_params.hash_alg->name, hsize, real_hash);
66 return -EBADMSG;
67}
68
69/*
70 * Verify a single data page against the file's Merkle tree.
71 *
72 * In principle, we need to verify the entire path to the root node. However,
73 * for efficiency the filesystem may cache the hash pages. Therefore we need
74 * only ascend the tree until an already-verified page is seen, as indicated by
75 * the PageChecked bit being set; then verify the path to that page.
76 *
77 * This code currently only supports the case where the verity block size is
78 * equal to PAGE_SIZE. Doing otherwise would be possible but tricky, since we
79 * wouldn't be able to use the PageChecked bit.
80 *
81 * Note that multiple processes may race to verify a hash page and mark it
82 * Checked, but it doesn't matter; the result will be the same either way.
83 *
84 * Return: true if the page is valid, else false.
85 */
86static bool verify_page(struct inode *inode, const struct fsverity_info *vi,
87 struct ahash_request *req, struct page *data_page,
88 unsigned long level0_ra_pages)
89{
90 const struct merkle_tree_params *params = &vi->tree_params;
91 const unsigned int hsize = params->digest_size;
92 const pgoff_t index = data_page->index;
93 int level;
94 u8 _want_hash[FS_VERITY_MAX_DIGEST_SIZE];
95 const u8 *want_hash;
96 u8 real_hash[FS_VERITY_MAX_DIGEST_SIZE];
97 struct page *hpages[FS_VERITY_MAX_LEVELS];
98 unsigned int hoffsets[FS_VERITY_MAX_LEVELS];
99 int err;
100
101 if (WARN_ON_ONCE(!PageLocked(data_page) || PageUptodate(data_page)))
102 return false;
103
104 pr_debug_ratelimited("Verifying data page %lu...\n", index);
105
106 /*
107 * Starting at the leaf level, ascend the tree saving hash pages along
108 * the way until we find a verified hash page, indicated by PageChecked;
109 * or until we reach the root.
110 */
111 for (level = 0; level < params->num_levels; level++) {
112 pgoff_t hindex;
113 unsigned int hoffset;
114 struct page *hpage;
115
116 hash_at_level(params, index, level, &hindex, &hoffset);
117
118 pr_debug_ratelimited("Level %d: hindex=%lu, hoffset=%u\n",
119 level, hindex, hoffset);
120
121 hpage = inode->i_sb->s_vop->read_merkle_tree_page(inode, hindex,
122 level == 0 ? level0_ra_pages : 0);
123 if (IS_ERR(hpage)) {
124 err = PTR_ERR(hpage);
125 fsverity_err(inode,
126 "Error %d reading Merkle tree page %lu",
127 err, hindex);
128 goto out;
129 }
130
131 if (PageChecked(hpage)) {
132 extract_hash(hpage, hoffset, hsize, _want_hash);
133 want_hash = _want_hash;
134 put_page(hpage);
135 pr_debug_ratelimited("Hash page already checked, want %s:%*phN\n",
136 params->hash_alg->name,
137 hsize, want_hash);
138 goto descend;
139 }
140 pr_debug_ratelimited("Hash page not yet checked\n");
141 hpages[level] = hpage;
142 hoffsets[level] = hoffset;
143 }
144
145 want_hash = vi->root_hash;
146 pr_debug("Want root hash: %s:%*phN\n",
147 params->hash_alg->name, hsize, want_hash);
148descend:
149 /* Descend the tree verifying hash pages */
150 for (; level > 0; level--) {
151 struct page *hpage = hpages[level - 1];
152 unsigned int hoffset = hoffsets[level - 1];
153
154 err = fsverity_hash_page(params, inode, req, hpage, real_hash);
155 if (err)
156 goto out;
157 err = cmp_hashes(vi, want_hash, real_hash, index, level - 1);
158 if (err)
159 goto out;
160 SetPageChecked(hpage);
161 extract_hash(hpage, hoffset, hsize, _want_hash);
162 want_hash = _want_hash;
163 put_page(hpage);
164 pr_debug("Verified hash page at level %d, now want %s:%*phN\n",
165 level - 1, params->hash_alg->name, hsize, want_hash);
166 }
167
168 /* Finally, verify the data page */
169 err = fsverity_hash_page(params, inode, req, data_page, real_hash);
170 if (err)
171 goto out;
172 err = cmp_hashes(vi, want_hash, real_hash, index, -1);
173out:
174 for (; level > 0; level--)
175 put_page(hpages[level - 1]);
176
177 return err == 0;
178}
179
180/**
181 * fsverity_verify_page() - verify a data page
182 * @page: the page to verity
183 *
184 * Verify a page that has just been read from a verity file. The page must be a
185 * pagecache page that is still locked and not yet uptodate.
186 *
187 * Return: true if the page is valid, else false.
188 */
189bool fsverity_verify_page(struct page *page)
190{
191 struct inode *inode = page->mapping->host;
192 const struct fsverity_info *vi = inode->i_verity_info;
193 struct ahash_request *req;
194 bool valid;
195
196 /* This allocation never fails, since it's mempool-backed. */
197 req = fsverity_alloc_hash_request(vi->tree_params.hash_alg, GFP_NOFS);
198
199 valid = verify_page(inode, vi, req, page, 0);
200
201 fsverity_free_hash_request(vi->tree_params.hash_alg, req);
202
203 return valid;
204}
205EXPORT_SYMBOL_GPL(fsverity_verify_page);
206
207#ifdef CONFIG_BLOCK
208/**
209 * fsverity_verify_bio() - verify a 'read' bio that has just completed
210 * @bio: the bio to verify
211 *
212 * Verify a set of pages that have just been read from a verity file. The pages
213 * must be pagecache pages that are still locked and not yet uptodate. Pages
214 * that fail verification are set to the Error state. Verification is skipped
215 * for pages already in the Error state, e.g. due to fscrypt decryption failure.
216 *
217 * This is a helper function for use by the ->readpages() method of filesystems
218 * that issue bios to read data directly into the page cache. Filesystems that
219 * populate the page cache without issuing bios (e.g. non block-based
220 * filesystems) must instead call fsverity_verify_page() directly on each page.
221 * All filesystems must also call fsverity_verify_page() on holes.
222 */
223void fsverity_verify_bio(struct bio *bio)
224{
225 struct inode *inode = bio_first_page_all(bio)->mapping->host;
226 const struct fsverity_info *vi = inode->i_verity_info;
227 const struct merkle_tree_params *params = &vi->tree_params;
228 struct ahash_request *req;
229 struct bio_vec *bv;
230 struct bvec_iter_all iter_all;
231 unsigned long max_ra_pages = 0;
232
233 /* This allocation never fails, since it's mempool-backed. */
234 req = fsverity_alloc_hash_request(params->hash_alg, GFP_NOFS);
235
236 if (bio->bi_opf & REQ_RAHEAD) {
237 /*
238 * If this bio is for data readahead, then we also do readahead
239 * of the first (largest) level of the Merkle tree. Namely,
240 * when a Merkle tree page is read, we also try to piggy-back on
241 * some additional pages -- up to 1/4 the number of data pages.
242 *
243 * This improves sequential read performance, as it greatly
244 * reduces the number of I/O requests made to the Merkle tree.
245 */
246 bio_for_each_segment_all(bv, bio, iter_all)
247 max_ra_pages++;
248 max_ra_pages /= 4;
249 }
250
251 bio_for_each_segment_all(bv, bio, iter_all) {
252 struct page *page = bv->bv_page;
253 unsigned long level0_index = page->index >> params->log_arity;
254 unsigned long level0_ra_pages =
255 min(max_ra_pages, params->level0_blocks - level0_index);
256
257 if (!PageError(page) &&
258 !verify_page(inode, vi, req, page, level0_ra_pages))
259 SetPageError(page);
260 }
261
262 fsverity_free_hash_request(params->hash_alg, req);
263}
264EXPORT_SYMBOL_GPL(fsverity_verify_bio);
265#endif /* CONFIG_BLOCK */
266
267/**
268 * fsverity_enqueue_verify_work() - enqueue work on the fs-verity workqueue
269 * @work: the work to enqueue
270 *
271 * Enqueue verification work for asynchronous processing.
272 */
273void fsverity_enqueue_verify_work(struct work_struct *work)
274{
275 queue_work(fsverity_read_workqueue, work);
276}
277EXPORT_SYMBOL_GPL(fsverity_enqueue_verify_work);
278
279int __init fsverity_init_workqueue(void)
280{
281 /*
282 * Use an unbound workqueue to allow bios to be verified in parallel
283 * even when they happen to complete on the same CPU. This sacrifices
284 * locality, but it's worthwhile since hashing is CPU-intensive.
285 *
286 * Also use a high-priority workqueue to prioritize verification work,
287 * which blocks reads from completing, over regular application tasks.
288 */
289 fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue",
290 WQ_UNBOUND | WQ_HIGHPRI,
291 num_online_cpus());
292 if (!fsverity_read_workqueue)
293 return -ENOMEM;
294 return 0;
295}
296
297void __init fsverity_exit_workqueue(void)
298{
299 destroy_workqueue(fsverity_read_workqueue);
300 fsverity_read_workqueue = NULL;
301}