xref: /linux/mm/kasan/init.c (revision c532de5a67a70f8533d495f8f2aaa9a0491c3ad0) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * This file contains KASAN shadow initialization code.
4  *
5  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
7  */
8 
9 #include <linux/memblock.h>
10 #include <linux/init.h>
11 #include <linux/kasan.h>
12 #include <linux/kernel.h>
13 #include <linux/mm.h>
14 #include <linux/pfn.h>
15 #include <linux/slab.h>
16 
17 #include <asm/page.h>
18 #include <asm/pgalloc.h>
19 
20 #include "kasan.h"
21 
22 /*
23  * This page serves two purposes:
24  *   - It used as early shadow memory. The entire shadow region populated
25  *     with this page, before we will be able to setup normal shadow memory.
26  *   - Latter it reused it as zero shadow to cover large ranges of memory
27  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
28  */
29 unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
30 
31 #if CONFIG_PGTABLE_LEVELS > 4
32 p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
33 static inline bool kasan_p4d_table(pgd_t pgd)
34 {
35 	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
36 }
37 #else
38 static inline bool kasan_p4d_table(pgd_t pgd)
39 {
40 	return false;
41 }
42 #endif
43 #if CONFIG_PGTABLE_LEVELS > 3
44 pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
45 static inline bool kasan_pud_table(p4d_t p4d)
46 {
47 	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
48 }
49 #else
50 static inline bool kasan_pud_table(p4d_t p4d)
51 {
52 	return false;
53 }
54 #endif
55 #if CONFIG_PGTABLE_LEVELS > 2
56 pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
57 static inline bool kasan_pmd_table(pud_t pud)
58 {
59 	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
60 }
61 #else
62 static inline bool kasan_pmd_table(pud_t pud)
63 {
64 	return false;
65 }
66 #endif
67 pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
68 	__page_aligned_bss;
69 
70 static inline bool kasan_pte_table(pmd_t pmd)
71 {
72 	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
73 }
74 
75 static inline bool kasan_early_shadow_page_entry(pte_t pte)
76 {
77 	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
78 }
79 
80 static __init void *early_alloc(size_t size, int node)
81 {
82 	void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
83 					   MEMBLOCK_ALLOC_ACCESSIBLE, node);
84 
85 	if (!ptr)
86 		panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
87 		      __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
88 
89 	return ptr;
90 }
91 
92 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
93 				unsigned long end)
94 {
95 	pte_t *pte = pte_offset_kernel(pmd, addr);
96 	pte_t zero_pte;
97 
98 	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
99 				PAGE_KERNEL);
100 	zero_pte = pte_wrprotect(zero_pte);
101 
102 	while (addr + PAGE_SIZE <= end) {
103 		set_pte_at(&init_mm, addr, pte, zero_pte);
104 		addr += PAGE_SIZE;
105 		pte = pte_offset_kernel(pmd, addr);
106 	}
107 }
108 
109 void __weak __meminit kernel_pte_init(void *addr)
110 {
111 }
112 
113 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
114 				unsigned long end)
115 {
116 	pmd_t *pmd = pmd_offset(pud, addr);
117 	unsigned long next;
118 
119 	do {
120 		next = pmd_addr_end(addr, end);
121 
122 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
123 			pmd_populate_kernel(&init_mm, pmd,
124 					lm_alias(kasan_early_shadow_pte));
125 			continue;
126 		}
127 
128 		if (pmd_none(*pmd)) {
129 			pte_t *p;
130 
131 			if (slab_is_available())
132 				p = pte_alloc_one_kernel(&init_mm);
133 			else {
134 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
135 				kernel_pte_init(p);
136 			}
137 			if (!p)
138 				return -ENOMEM;
139 
140 			pmd_populate_kernel(&init_mm, pmd, p);
141 		}
142 		zero_pte_populate(pmd, addr, next);
143 	} while (pmd++, addr = next, addr != end);
144 
145 	return 0;
146 }
147 
148 void __weak __meminit pmd_init(void *addr)
149 {
150 }
151 
152 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
153 				unsigned long end)
154 {
155 	pud_t *pud = pud_offset(p4d, addr);
156 	unsigned long next;
157 
158 	do {
159 		next = pud_addr_end(addr, end);
160 		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
161 			pmd_t *pmd;
162 
163 			pud_populate(&init_mm, pud,
164 					lm_alias(kasan_early_shadow_pmd));
165 			pmd = pmd_offset(pud, addr);
166 			pmd_populate_kernel(&init_mm, pmd,
167 					lm_alias(kasan_early_shadow_pte));
168 			continue;
169 		}
170 
171 		if (pud_none(*pud)) {
172 			pmd_t *p;
173 
174 			if (slab_is_available()) {
175 				p = pmd_alloc(&init_mm, pud, addr);
176 				if (!p)
177 					return -ENOMEM;
178 			} else {
179 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
180 				pmd_init(p);
181 				pud_populate(&init_mm, pud, p);
182 			}
183 		}
184 		zero_pmd_populate(pud, addr, next);
185 	} while (pud++, addr = next, addr != end);
186 
187 	return 0;
188 }
189 
190 void __weak __meminit pud_init(void *addr)
191 {
192 }
193 
194 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
195 				unsigned long end)
196 {
197 	p4d_t *p4d = p4d_offset(pgd, addr);
198 	unsigned long next;
199 
200 	do {
201 		next = p4d_addr_end(addr, end);
202 		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
203 			pud_t *pud;
204 			pmd_t *pmd;
205 
206 			p4d_populate(&init_mm, p4d,
207 					lm_alias(kasan_early_shadow_pud));
208 			pud = pud_offset(p4d, addr);
209 			pud_populate(&init_mm, pud,
210 					lm_alias(kasan_early_shadow_pmd));
211 			pmd = pmd_offset(pud, addr);
212 			pmd_populate_kernel(&init_mm, pmd,
213 					lm_alias(kasan_early_shadow_pte));
214 			continue;
215 		}
216 
217 		if (p4d_none(*p4d)) {
218 			pud_t *p;
219 
220 			if (slab_is_available()) {
221 				p = pud_alloc(&init_mm, p4d, addr);
222 				if (!p)
223 					return -ENOMEM;
224 			} else {
225 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
226 				pud_init(p);
227 				p4d_populate(&init_mm, p4d, p);
228 			}
229 		}
230 		zero_pud_populate(p4d, addr, next);
231 	} while (p4d++, addr = next, addr != end);
232 
233 	return 0;
234 }
235 
236 /**
237  * kasan_populate_early_shadow - populate shadow memory region with
238  *                               kasan_early_shadow_page
239  * @shadow_start: start of the memory range to populate
240  * @shadow_end: end of the memory range to populate
241  */
242 int __ref kasan_populate_early_shadow(const void *shadow_start,
243 					const void *shadow_end)
244 {
245 	unsigned long addr = (unsigned long)shadow_start;
246 	unsigned long end = (unsigned long)shadow_end;
247 	pgd_t *pgd = pgd_offset_k(addr);
248 	unsigned long next;
249 
250 	do {
251 		next = pgd_addr_end(addr, end);
252 
253 		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
254 			p4d_t *p4d;
255 			pud_t *pud;
256 			pmd_t *pmd;
257 
258 			/*
259 			 * kasan_early_shadow_pud should be populated with pmds
260 			 * at this moment.
261 			 * [pud,pmd]_populate*() below needed only for
262 			 * 3,2 - level page tables where we don't have
263 			 * puds,pmds, so pgd_populate(), pud_populate()
264 			 * is noops.
265 			 */
266 			pgd_populate(&init_mm, pgd,
267 					lm_alias(kasan_early_shadow_p4d));
268 			p4d = p4d_offset(pgd, addr);
269 			p4d_populate(&init_mm, p4d,
270 					lm_alias(kasan_early_shadow_pud));
271 			pud = pud_offset(p4d, addr);
272 			pud_populate(&init_mm, pud,
273 					lm_alias(kasan_early_shadow_pmd));
274 			pmd = pmd_offset(pud, addr);
275 			pmd_populate_kernel(&init_mm, pmd,
276 					lm_alias(kasan_early_shadow_pte));
277 			continue;
278 		}
279 
280 		if (pgd_none(*pgd)) {
281 			p4d_t *p;
282 
283 			if (slab_is_available()) {
284 				p = p4d_alloc(&init_mm, pgd, addr);
285 				if (!p)
286 					return -ENOMEM;
287 			} else {
288 				pgd_populate(&init_mm, pgd,
289 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
290 			}
291 		}
292 		zero_p4d_populate(pgd, addr, next);
293 	} while (pgd++, addr = next, addr != end);
294 
295 	return 0;
296 }
297 
298 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
299 {
300 	pte_t *pte;
301 	int i;
302 
303 	for (i = 0; i < PTRS_PER_PTE; i++) {
304 		pte = pte_start + i;
305 		if (!pte_none(ptep_get(pte)))
306 			return;
307 	}
308 
309 	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
310 	pmd_clear(pmd);
311 }
312 
313 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
314 {
315 	pmd_t *pmd;
316 	int i;
317 
318 	for (i = 0; i < PTRS_PER_PMD; i++) {
319 		pmd = pmd_start + i;
320 		if (!pmd_none(*pmd))
321 			return;
322 	}
323 
324 	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
325 	pud_clear(pud);
326 }
327 
328 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
329 {
330 	pud_t *pud;
331 	int i;
332 
333 	for (i = 0; i < PTRS_PER_PUD; i++) {
334 		pud = pud_start + i;
335 		if (!pud_none(*pud))
336 			return;
337 	}
338 
339 	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
340 	p4d_clear(p4d);
341 }
342 
343 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
344 {
345 	p4d_t *p4d;
346 	int i;
347 
348 	for (i = 0; i < PTRS_PER_P4D; i++) {
349 		p4d = p4d_start + i;
350 		if (!p4d_none(*p4d))
351 			return;
352 	}
353 
354 	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
355 	pgd_clear(pgd);
356 }
357 
358 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
359 				unsigned long end)
360 {
361 	unsigned long next;
362 	pte_t ptent;
363 
364 	for (; addr < end; addr = next, pte++) {
365 		next = (addr + PAGE_SIZE) & PAGE_MASK;
366 		if (next > end)
367 			next = end;
368 
369 		ptent = ptep_get(pte);
370 
371 		if (!pte_present(ptent))
372 			continue;
373 
374 		if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
375 			continue;
376 		pte_clear(&init_mm, addr, pte);
377 	}
378 }
379 
380 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
381 				unsigned long end)
382 {
383 	unsigned long next;
384 
385 	for (; addr < end; addr = next, pmd++) {
386 		pte_t *pte;
387 
388 		next = pmd_addr_end(addr, end);
389 
390 		if (!pmd_present(*pmd))
391 			continue;
392 
393 		if (kasan_pte_table(*pmd)) {
394 			if (IS_ALIGNED(addr, PMD_SIZE) &&
395 			    IS_ALIGNED(next, PMD_SIZE)) {
396 				pmd_clear(pmd);
397 				continue;
398 			}
399 		}
400 		pte = pte_offset_kernel(pmd, addr);
401 		kasan_remove_pte_table(pte, addr, next);
402 		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
403 	}
404 }
405 
406 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
407 				unsigned long end)
408 {
409 	unsigned long next;
410 
411 	for (; addr < end; addr = next, pud++) {
412 		pmd_t *pmd, *pmd_base;
413 
414 		next = pud_addr_end(addr, end);
415 
416 		if (!pud_present(*pud))
417 			continue;
418 
419 		if (kasan_pmd_table(*pud)) {
420 			if (IS_ALIGNED(addr, PUD_SIZE) &&
421 			    IS_ALIGNED(next, PUD_SIZE)) {
422 				pud_clear(pud);
423 				continue;
424 			}
425 		}
426 		pmd = pmd_offset(pud, addr);
427 		pmd_base = pmd_offset(pud, 0);
428 		kasan_remove_pmd_table(pmd, addr, next);
429 		kasan_free_pmd(pmd_base, pud);
430 	}
431 }
432 
433 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
434 				unsigned long end)
435 {
436 	unsigned long next;
437 
438 	for (; addr < end; addr = next, p4d++) {
439 		pud_t *pud;
440 
441 		next = p4d_addr_end(addr, end);
442 
443 		if (!p4d_present(*p4d))
444 			continue;
445 
446 		if (kasan_pud_table(*p4d)) {
447 			if (IS_ALIGNED(addr, P4D_SIZE) &&
448 			    IS_ALIGNED(next, P4D_SIZE)) {
449 				p4d_clear(p4d);
450 				continue;
451 			}
452 		}
453 		pud = pud_offset(p4d, addr);
454 		kasan_remove_pud_table(pud, addr, next);
455 		kasan_free_pud(pud_offset(p4d, 0), p4d);
456 	}
457 }
458 
459 void kasan_remove_zero_shadow(void *start, unsigned long size)
460 {
461 	unsigned long addr, end, next;
462 	pgd_t *pgd;
463 
464 	addr = (unsigned long)kasan_mem_to_shadow(start);
465 	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
466 
467 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
468 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
469 		return;
470 
471 	for (; addr < end; addr = next) {
472 		p4d_t *p4d;
473 
474 		next = pgd_addr_end(addr, end);
475 
476 		pgd = pgd_offset_k(addr);
477 		if (!pgd_present(*pgd))
478 			continue;
479 
480 		if (kasan_p4d_table(*pgd)) {
481 			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
482 			    IS_ALIGNED(next, PGDIR_SIZE)) {
483 				pgd_clear(pgd);
484 				continue;
485 			}
486 		}
487 
488 		p4d = p4d_offset(pgd, addr);
489 		kasan_remove_p4d_table(p4d, addr, next);
490 		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
491 	}
492 }
493 
494 int kasan_add_zero_shadow(void *start, unsigned long size)
495 {
496 	int ret;
497 	void *shadow_start, *shadow_end;
498 
499 	shadow_start = kasan_mem_to_shadow(start);
500 	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
501 
502 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
503 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
504 		return -EINVAL;
505 
506 	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
507 	if (ret)
508 		kasan_remove_zero_shadow(start, size);
509 	return ret;
510 }
511