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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * KMSAN hooks for kernel subsystems.
4 *
5 * These functions handle creation of KMSAN metadata for memory allocations.
6 *
7 * Copyright (C) 2018-2022 Google LLC
8 * Author: Alexander Potapenko <glider@google.com>
9 *
10 */
11
12#include <linux/cacheflush.h>
13#include <linux/dma-direction.h>
14#include <linux/gfp.h>
15#include <linux/kmsan.h>
16#include <linux/mm.h>
17#include <linux/mm_types.h>
18#include <linux/scatterlist.h>
19#include <linux/slab.h>
20#include <linux/uaccess.h>
21#include <linux/usb.h>
22
23#include "../internal.h"
24#include "../slab.h"
25#include "kmsan.h"
26
27/*
28 * Instrumented functions shouldn't be called under
29 * kmsan_enter_runtime()/kmsan_leave_runtime(), because this will lead to
30 * skipping effects of functions like memset() inside instrumented code.
31 */
32
33void kmsan_task_create(struct task_struct *task)
34{
35 kmsan_enter_runtime();
36 kmsan_internal_task_create(task);
37 kmsan_leave_runtime();
38}
39
40void kmsan_task_exit(struct task_struct *task)
41{
42 struct kmsan_ctx *ctx = &task->kmsan_ctx;
43
44 if (!kmsan_enabled || kmsan_in_runtime())
45 return;
46
47 ctx->allow_reporting = false;
48}
49
50void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags)
51{
52 if (unlikely(object == NULL))
53 return;
54 if (!kmsan_enabled || kmsan_in_runtime())
55 return;
56 /*
57 * There's a ctor or this is an RCU cache - do nothing. The memory
58 * status hasn't changed since last use.
59 */
60 if (s->ctor || (s->flags & SLAB_TYPESAFE_BY_RCU))
61 return;
62
63 kmsan_enter_runtime();
64 if (flags & __GFP_ZERO)
65 kmsan_internal_unpoison_memory(object, s->object_size,
66 KMSAN_POISON_CHECK);
67 else
68 kmsan_internal_poison_memory(object, s->object_size, flags,
69 KMSAN_POISON_CHECK);
70 kmsan_leave_runtime();
71}
72
73void kmsan_slab_free(struct kmem_cache *s, void *object)
74{
75 if (!kmsan_enabled || kmsan_in_runtime())
76 return;
77
78 /* RCU slabs could be legally used after free within the RCU period */
79 if (unlikely(s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)))
80 return;
81 /*
82 * If there's a constructor, freed memory must remain in the same state
83 * until the next allocation. We cannot save its state to detect
84 * use-after-free bugs, instead we just keep it unpoisoned.
85 */
86 if (s->ctor)
87 return;
88 kmsan_enter_runtime();
89 kmsan_internal_poison_memory(object, s->object_size, GFP_KERNEL,
90 KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
91 kmsan_leave_runtime();
92}
93
94void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
95{
96 if (unlikely(ptr == NULL))
97 return;
98 if (!kmsan_enabled || kmsan_in_runtime())
99 return;
100 kmsan_enter_runtime();
101 if (flags & __GFP_ZERO)
102 kmsan_internal_unpoison_memory((void *)ptr, size,
103 /*checked*/ true);
104 else
105 kmsan_internal_poison_memory((void *)ptr, size, flags,
106 KMSAN_POISON_CHECK);
107 kmsan_leave_runtime();
108}
109
110void kmsan_kfree_large(const void *ptr)
111{
112 struct page *page;
113
114 if (!kmsan_enabled || kmsan_in_runtime())
115 return;
116 kmsan_enter_runtime();
117 page = virt_to_head_page((void *)ptr);
118 KMSAN_WARN_ON(ptr != page_address(page));
119 kmsan_internal_poison_memory((void *)ptr,
120 PAGE_SIZE << compound_order(page),
121 GFP_KERNEL,
122 KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
123 kmsan_leave_runtime();
124}
125
126static unsigned long vmalloc_shadow(unsigned long addr)
127{
128 return (unsigned long)kmsan_get_metadata((void *)addr,
129 KMSAN_META_SHADOW);
130}
131
132static unsigned long vmalloc_origin(unsigned long addr)
133{
134 return (unsigned long)kmsan_get_metadata((void *)addr,
135 KMSAN_META_ORIGIN);
136}
137
138void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end)
139{
140 __vunmap_range_noflush(vmalloc_shadow(start), vmalloc_shadow(end));
141 __vunmap_range_noflush(vmalloc_origin(start), vmalloc_origin(end));
142 flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
143 flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
144}
145
146/*
147 * This function creates new shadow/origin pages for the physical pages mapped
148 * into the virtual memory. If those physical pages already had shadow/origin,
149 * those are ignored.
150 */
151void kmsan_ioremap_page_range(unsigned long start, unsigned long end,
152 phys_addr_t phys_addr, pgprot_t prot,
153 unsigned int page_shift)
154{
155 gfp_t gfp_mask = GFP_KERNEL | __GFP_ZERO;
156 struct page *shadow, *origin;
157 unsigned long off = 0;
158 int nr;
159
160 if (!kmsan_enabled || kmsan_in_runtime())
161 return;
162
163 nr = (end - start) / PAGE_SIZE;
164 kmsan_enter_runtime();
165 for (int i = 0; i < nr; i++, off += PAGE_SIZE) {
166 shadow = alloc_pages(gfp_mask, 1);
167 origin = alloc_pages(gfp_mask, 1);
168 __vmap_pages_range_noflush(
169 vmalloc_shadow(start + off),
170 vmalloc_shadow(start + off + PAGE_SIZE), prot, &shadow,
171 PAGE_SHIFT);
172 __vmap_pages_range_noflush(
173 vmalloc_origin(start + off),
174 vmalloc_origin(start + off + PAGE_SIZE), prot, &origin,
175 PAGE_SHIFT);
176 }
177 flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
178 flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
179 kmsan_leave_runtime();
180}
181
182void kmsan_iounmap_page_range(unsigned long start, unsigned long end)
183{
184 unsigned long v_shadow, v_origin;
185 struct page *shadow, *origin;
186 int nr;
187
188 if (!kmsan_enabled || kmsan_in_runtime())
189 return;
190
191 nr = (end - start) / PAGE_SIZE;
192 kmsan_enter_runtime();
193 v_shadow = (unsigned long)vmalloc_shadow(start);
194 v_origin = (unsigned long)vmalloc_origin(start);
195 for (int i = 0; i < nr;
196 i++, v_shadow += PAGE_SIZE, v_origin += PAGE_SIZE) {
197 shadow = kmsan_vmalloc_to_page_or_null((void *)v_shadow);
198 origin = kmsan_vmalloc_to_page_or_null((void *)v_origin);
199 __vunmap_range_noflush(v_shadow, vmalloc_shadow(end));
200 __vunmap_range_noflush(v_origin, vmalloc_origin(end));
201 if (shadow)
202 __free_pages(shadow, 1);
203 if (origin)
204 __free_pages(origin, 1);
205 }
206 flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
207 flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
208 kmsan_leave_runtime();
209}
210
211void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
212 size_t left)
213{
214 unsigned long ua_flags;
215
216 if (!kmsan_enabled || kmsan_in_runtime())
217 return;
218 /*
219 * At this point we've copied the memory already. It's hard to check it
220 * before copying, as the size of actually copied buffer is unknown.
221 */
222
223 /* copy_to_user() may copy zero bytes. No need to check. */
224 if (!to_copy)
225 return;
226 /* Or maybe copy_to_user() failed to copy anything. */
227 if (to_copy <= left)
228 return;
229
230 ua_flags = user_access_save();
231 if ((u64)to < TASK_SIZE) {
232 /* This is a user memory access, check it. */
233 kmsan_internal_check_memory((void *)from, to_copy - left, to,
234 REASON_COPY_TO_USER);
235 } else {
236 /* Otherwise this is a kernel memory access. This happens when a
237 * compat syscall passes an argument allocated on the kernel
238 * stack to a real syscall.
239 * Don't check anything, just copy the shadow of the copied
240 * bytes.
241 */
242 kmsan_internal_memmove_metadata((void *)to, (void *)from,
243 to_copy - left);
244 }
245 user_access_restore(ua_flags);
246}
247EXPORT_SYMBOL(kmsan_copy_to_user);
248
249/* Helper function to check an URB. */
250void kmsan_handle_urb(const struct urb *urb, bool is_out)
251{
252 if (!urb)
253 return;
254 if (is_out)
255 kmsan_internal_check_memory(urb->transfer_buffer,
256 urb->transfer_buffer_length,
257 /*user_addr*/ 0, REASON_SUBMIT_URB);
258 else
259 kmsan_internal_unpoison_memory(urb->transfer_buffer,
260 urb->transfer_buffer_length,
261 /*checked*/ false);
262}
263EXPORT_SYMBOL_GPL(kmsan_handle_urb);
264
265static void kmsan_handle_dma_page(const void *addr, size_t size,
266 enum dma_data_direction dir)
267{
268 switch (dir) {
269 case DMA_BIDIRECTIONAL:
270 kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
271 REASON_ANY);
272 kmsan_internal_unpoison_memory((void *)addr, size,
273 /*checked*/ false);
274 break;
275 case DMA_TO_DEVICE:
276 kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
277 REASON_ANY);
278 break;
279 case DMA_FROM_DEVICE:
280 kmsan_internal_unpoison_memory((void *)addr, size,
281 /*checked*/ false);
282 break;
283 case DMA_NONE:
284 break;
285 }
286}
287
288/* Helper function to handle DMA data transfers. */
289void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
290 enum dma_data_direction dir)
291{
292 u64 page_offset, to_go, addr;
293
294 if (PageHighMem(page))
295 return;
296 addr = (u64)page_address(page) + offset;
297 /*
298 * The kernel may occasionally give us adjacent DMA pages not belonging
299 * to the same allocation. Process them separately to avoid triggering
300 * internal KMSAN checks.
301 */
302 while (size > 0) {
303 page_offset = addr % PAGE_SIZE;
304 to_go = min(PAGE_SIZE - page_offset, (u64)size);
305 kmsan_handle_dma_page((void *)addr, to_go, dir);
306 addr += to_go;
307 size -= to_go;
308 }
309}
310
311void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
312 enum dma_data_direction dir)
313{
314 struct scatterlist *item;
315 int i;
316
317 for_each_sg(sg, item, nents, i)
318 kmsan_handle_dma(sg_page(item), item->offset, item->length,
319 dir);
320}
321
322/* Functions from kmsan-checks.h follow. */
323void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)
324{
325 if (!kmsan_enabled || kmsan_in_runtime())
326 return;
327 kmsan_enter_runtime();
328 /* The users may want to poison/unpoison random memory. */
329 kmsan_internal_poison_memory((void *)address, size, flags,
330 KMSAN_POISON_NOCHECK);
331 kmsan_leave_runtime();
332}
333EXPORT_SYMBOL(kmsan_poison_memory);
334
335void kmsan_unpoison_memory(const void *address, size_t size)
336{
337 unsigned long ua_flags;
338
339 if (!kmsan_enabled || kmsan_in_runtime())
340 return;
341
342 ua_flags = user_access_save();
343 kmsan_enter_runtime();
344 /* The users may want to poison/unpoison random memory. */
345 kmsan_internal_unpoison_memory((void *)address, size,
346 KMSAN_POISON_NOCHECK);
347 kmsan_leave_runtime();
348 user_access_restore(ua_flags);
349}
350EXPORT_SYMBOL(kmsan_unpoison_memory);
351
352/*
353 * Version of kmsan_unpoison_memory() that can be called from within the KMSAN
354 * runtime.
355 *
356 * Non-instrumented IRQ entry functions receive struct pt_regs from assembly
357 * code. Those regs need to be unpoisoned, otherwise using them will result in
358 * false positives.
359 * Using kmsan_unpoison_memory() is not an option in entry code, because the
360 * return value of in_task() is inconsistent - as a result, certain calls to
361 * kmsan_unpoison_memory() are ignored. kmsan_unpoison_entry_regs() ensures that
362 * the registers are unpoisoned even if kmsan_in_runtime() is true in the early
363 * entry code.
364 */
365void kmsan_unpoison_entry_regs(const struct pt_regs *regs)
366{
367 unsigned long ua_flags;
368
369 if (!kmsan_enabled)
370 return;
371
372 ua_flags = user_access_save();
373 kmsan_internal_unpoison_memory((void *)regs, sizeof(*regs),
374 KMSAN_POISON_NOCHECK);
375 user_access_restore(ua_flags);
376}
377
378void kmsan_check_memory(const void *addr, size_t size)
379{
380 if (!kmsan_enabled)
381 return;
382 return kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
383 REASON_ANY);
384}
385EXPORT_SYMBOL(kmsan_check_memory);