xref: /linux/mm/kasan/init.c (revision c34e9ab9a612ee8b18273398ef75c207b01f516d) 
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 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
110 				unsigned long end)
111 {
112 	pmd_t *pmd = pmd_offset(pud, addr);
113 	unsigned long next;
114 
115 	do {
116 		next = pmd_addr_end(addr, end);
117 
118 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
119 			pmd_populate_kernel(&init_mm, pmd,
120 					lm_alias(kasan_early_shadow_pte));
121 			continue;
122 		}
123 
124 		if (pmd_none(*pmd)) {
125 			pte_t *p;
126 
127 			if (slab_is_available())
128 				p = pte_alloc_one_kernel(&init_mm);
129 			else {
130 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
131 				kernel_pte_init(p);
132 			}
133 			if (!p)
134 				return -ENOMEM;
135 
136 			pmd_populate_kernel(&init_mm, pmd, p);
137 		}
138 		zero_pte_populate(pmd, addr, next);
139 	} while (pmd++, addr = next, addr != end);
140 
141 	return 0;
142 }
143 
144 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
145 				unsigned long end)
146 {
147 	pud_t *pud = pud_offset(p4d, addr);
148 	unsigned long next;
149 
150 	do {
151 		next = pud_addr_end(addr, end);
152 		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
153 			pmd_t *pmd;
154 
155 			pud_populate(&init_mm, pud,
156 					lm_alias(kasan_early_shadow_pmd));
157 			pmd = pmd_offset(pud, addr);
158 			pmd_populate_kernel(&init_mm, pmd,
159 					lm_alias(kasan_early_shadow_pte));
160 			continue;
161 		}
162 
163 		if (pud_none(*pud)) {
164 			pmd_t *p;
165 
166 			if (slab_is_available()) {
167 				p = pmd_alloc(&init_mm, pud, addr);
168 				if (!p)
169 					return -ENOMEM;
170 			} else {
171 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
172 				pmd_init(p);
173 				pud_populate(&init_mm, pud, p);
174 			}
175 		}
176 		zero_pmd_populate(pud, addr, next);
177 	} while (pud++, addr = next, addr != end);
178 
179 	return 0;
180 }
181 
182 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
183 				unsigned long end)
184 {
185 	p4d_t *p4d = p4d_offset(pgd, addr);
186 	unsigned long next;
187 
188 	do {
189 		next = p4d_addr_end(addr, end);
190 		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
191 			pud_t *pud;
192 			pmd_t *pmd;
193 
194 			p4d_populate(&init_mm, p4d,
195 					lm_alias(kasan_early_shadow_pud));
196 			pud = pud_offset(p4d, addr);
197 			pud_populate(&init_mm, pud,
198 					lm_alias(kasan_early_shadow_pmd));
199 			pmd = pmd_offset(pud, addr);
200 			pmd_populate_kernel(&init_mm, pmd,
201 					lm_alias(kasan_early_shadow_pte));
202 			continue;
203 		}
204 
205 		if (p4d_none(*p4d)) {
206 			pud_t *p;
207 
208 			if (slab_is_available()) {
209 				p = pud_alloc(&init_mm, p4d, addr);
210 				if (!p)
211 					return -ENOMEM;
212 			} else {
213 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
214 				pud_init(p);
215 				p4d_populate(&init_mm, p4d, p);
216 			}
217 		}
218 		zero_pud_populate(p4d, addr, next);
219 	} while (p4d++, addr = next, addr != end);
220 
221 	return 0;
222 }
223 
224 /**
225  * kasan_populate_early_shadow - populate shadow memory region with
226  *                               kasan_early_shadow_page
227  * @shadow_start: start of the memory range to populate
228  * @shadow_end: end of the memory range to populate
229  */
230 int __ref kasan_populate_early_shadow(const void *shadow_start,
231 					const void *shadow_end)
232 {
233 	unsigned long addr = (unsigned long)shadow_start;
234 	unsigned long end = (unsigned long)shadow_end;
235 	pgd_t *pgd = pgd_offset_k(addr);
236 	unsigned long next;
237 
238 	do {
239 		next = pgd_addr_end(addr, end);
240 
241 		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
242 			p4d_t *p4d;
243 			pud_t *pud;
244 			pmd_t *pmd;
245 
246 			/*
247 			 * kasan_early_shadow_pud should be populated with pmds
248 			 * at this moment.
249 			 * [pud,pmd]_populate*() below needed only for
250 			 * 3,2 - level page tables where we don't have
251 			 * puds,pmds, so pgd_populate(), pud_populate()
252 			 * is noops.
253 			 */
254 			pgd_populate(&init_mm, pgd,
255 					lm_alias(kasan_early_shadow_p4d));
256 			p4d = p4d_offset(pgd, addr);
257 			p4d_populate(&init_mm, p4d,
258 					lm_alias(kasan_early_shadow_pud));
259 			pud = pud_offset(p4d, addr);
260 			pud_populate(&init_mm, pud,
261 					lm_alias(kasan_early_shadow_pmd));
262 			pmd = pmd_offset(pud, addr);
263 			pmd_populate_kernel(&init_mm, pmd,
264 					lm_alias(kasan_early_shadow_pte));
265 			continue;
266 		}
267 
268 		if (pgd_none(*pgd)) {
269 			p4d_t *p;
270 
271 			if (slab_is_available()) {
272 				p = p4d_alloc(&init_mm, pgd, addr);
273 				if (!p)
274 					return -ENOMEM;
275 			} else {
276 				pgd_populate(&init_mm, pgd,
277 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
278 			}
279 		}
280 		zero_p4d_populate(pgd, addr, next);
281 	} while (pgd++, addr = next, addr != end);
282 
283 	return 0;
284 }
285 
286 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
287 {
288 	pte_t *pte;
289 	int i;
290 
291 	for (i = 0; i < PTRS_PER_PTE; i++) {
292 		pte = pte_start + i;
293 		if (!pte_none(ptep_get(pte)))
294 			return;
295 	}
296 
297 	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
298 	pmd_clear(pmd);
299 }
300 
301 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
302 {
303 	pmd_t *pmd;
304 	int i;
305 
306 	for (i = 0; i < PTRS_PER_PMD; i++) {
307 		pmd = pmd_start + i;
308 		if (!pmd_none(*pmd))
309 			return;
310 	}
311 
312 	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
313 	pud_clear(pud);
314 }
315 
316 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
317 {
318 	pud_t *pud;
319 	int i;
320 
321 	for (i = 0; i < PTRS_PER_PUD; i++) {
322 		pud = pud_start + i;
323 		if (!pud_none(*pud))
324 			return;
325 	}
326 
327 	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
328 	p4d_clear(p4d);
329 }
330 
331 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
332 {
333 	p4d_t *p4d;
334 	int i;
335 
336 	for (i = 0; i < PTRS_PER_P4D; i++) {
337 		p4d = p4d_start + i;
338 		if (!p4d_none(*p4d))
339 			return;
340 	}
341 
342 	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
343 	pgd_clear(pgd);
344 }
345 
346 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
347 				unsigned long end)
348 {
349 	unsigned long next;
350 	pte_t ptent;
351 
352 	for (; addr < end; addr = next, pte++) {
353 		next = (addr + PAGE_SIZE) & PAGE_MASK;
354 		if (next > end)
355 			next = end;
356 
357 		ptent = ptep_get(pte);
358 
359 		if (!pte_present(ptent))
360 			continue;
361 
362 		if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
363 			continue;
364 		pte_clear(&init_mm, addr, pte);
365 	}
366 }
367 
368 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
369 				unsigned long end)
370 {
371 	unsigned long next;
372 
373 	for (; addr < end; addr = next, pmd++) {
374 		pte_t *pte;
375 
376 		next = pmd_addr_end(addr, end);
377 
378 		if (!pmd_present(*pmd))
379 			continue;
380 
381 		if (kasan_pte_table(*pmd)) {
382 			if (IS_ALIGNED(addr, PMD_SIZE) &&
383 			    IS_ALIGNED(next, PMD_SIZE)) {
384 				pmd_clear(pmd);
385 				continue;
386 			}
387 		}
388 		pte = pte_offset_kernel(pmd, addr);
389 		kasan_remove_pte_table(pte, addr, next);
390 		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
391 	}
392 }
393 
394 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
395 				unsigned long end)
396 {
397 	unsigned long next;
398 
399 	for (; addr < end; addr = next, pud++) {
400 		pmd_t *pmd, *pmd_base;
401 
402 		next = pud_addr_end(addr, end);
403 
404 		if (!pud_present(*pud))
405 			continue;
406 
407 		if (kasan_pmd_table(*pud)) {
408 			if (IS_ALIGNED(addr, PUD_SIZE) &&
409 			    IS_ALIGNED(next, PUD_SIZE)) {
410 				pud_clear(pud);
411 				continue;
412 			}
413 		}
414 		pmd = pmd_offset(pud, addr);
415 		pmd_base = pmd_offset(pud, 0);
416 		kasan_remove_pmd_table(pmd, addr, next);
417 		kasan_free_pmd(pmd_base, pud);
418 	}
419 }
420 
421 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
422 				unsigned long end)
423 {
424 	unsigned long next;
425 
426 	for (; addr < end; addr = next, p4d++) {
427 		pud_t *pud;
428 
429 		next = p4d_addr_end(addr, end);
430 
431 		if (!p4d_present(*p4d))
432 			continue;
433 
434 		if (kasan_pud_table(*p4d)) {
435 			if (IS_ALIGNED(addr, P4D_SIZE) &&
436 			    IS_ALIGNED(next, P4D_SIZE)) {
437 				p4d_clear(p4d);
438 				continue;
439 			}
440 		}
441 		pud = pud_offset(p4d, addr);
442 		kasan_remove_pud_table(pud, addr, next);
443 		kasan_free_pud(pud_offset(p4d, 0), p4d);
444 	}
445 }
446 
447 void kasan_remove_zero_shadow(void *start, unsigned long size)
448 {
449 	unsigned long addr, end, next;
450 	pgd_t *pgd;
451 
452 	addr = (unsigned long)kasan_mem_to_shadow(start);
453 	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
454 
455 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
456 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
457 		return;
458 
459 	for (; addr < end; addr = next) {
460 		p4d_t *p4d;
461 
462 		next = pgd_addr_end(addr, end);
463 
464 		pgd = pgd_offset_k(addr);
465 		if (!pgd_present(*pgd))
466 			continue;
467 
468 		if (kasan_p4d_table(*pgd)) {
469 			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
470 			    IS_ALIGNED(next, PGDIR_SIZE)) {
471 				pgd_clear(pgd);
472 				continue;
473 			}
474 		}
475 
476 		p4d = p4d_offset(pgd, addr);
477 		kasan_remove_p4d_table(p4d, addr, next);
478 		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
479 	}
480 }
481 
482 int kasan_add_zero_shadow(void *start, unsigned long size)
483 {
484 	int ret;
485 	void *shadow_start, *shadow_end;
486 
487 	shadow_start = kasan_mem_to_shadow(start);
488 	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
489 
490 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
491 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
492 		return -EINVAL;
493 
494 	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
495 	if (ret)
496 		kasan_remove_zero_shadow(start, size);
497 	return ret;
498 }
499