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(address: object, size: s->object_size,
66 KMSAN_POISON_CHECK);
67 else
68 kmsan_internal_poison_memory(address: object, size: 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(address: object, size: 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(address: (void *)ptr, size,
103 /*checked*/ true);
104 else
105 kmsan_internal_poison_memory(address: (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(x: (void *)ptr);
118 KMSAN_WARN_ON(ptr != page_address(page));
119 kmsan_internal_poison_memory(address: (void *)ptr,
120 size: page_size(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(addr: (void *)addr,
129 KMSAN_META_SHADOW);
130}
131
132static unsigned long vmalloc_origin(unsigned long addr)
133{
134 return (unsigned long)kmsan_get_metadata(addr: (void *)addr,
135 KMSAN_META_ORIGIN);
136}
137
138void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end)
139{
140 __vunmap_range_noflush(start: vmalloc_shadow(addr: start), end: vmalloc_shadow(addr: end));
141 __vunmap_range_noflush(start: vmalloc_origin(addr: start), end: vmalloc_origin(addr: end));
142 flush_cache_vmap(start: vmalloc_shadow(addr: start), end: vmalloc_shadow(addr: end));
143 flush_cache_vmap(start: vmalloc_origin(addr: start), end: vmalloc_origin(addr: 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 */
151int 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, err = 0, clean = 0, mapped;
159
160 if (!kmsan_enabled || kmsan_in_runtime())
161 return 0;
162
163 nr = (end - start) / PAGE_SIZE;
164 kmsan_enter_runtime();
165 for (int i = 0; i < nr; i++, off += PAGE_SIZE, clean = i) {
166 shadow = alloc_pages(gfp: gfp_mask, order: 1);
167 origin = alloc_pages(gfp: gfp_mask, order: 1);
168 if (!shadow || !origin) {
169 err = -ENOMEM;
170 goto ret;
171 }
172 mapped = __vmap_pages_range_noflush(
173 addr: vmalloc_shadow(addr: start + off),
174 end: vmalloc_shadow(addr: start + off + PAGE_SIZE), prot, pages: &shadow,
175 PAGE_SHIFT);
176 if (mapped) {
177 err = mapped;
178 goto ret;
179 }
180 shadow = NULL;
181 mapped = __vmap_pages_range_noflush(
182 addr: vmalloc_origin(addr: start + off),
183 end: vmalloc_origin(addr: start + off + PAGE_SIZE), prot, pages: &origin,
184 PAGE_SHIFT);
185 if (mapped) {
186 __vunmap_range_noflush(
187 start: vmalloc_shadow(addr: start + off),
188 end: vmalloc_shadow(addr: start + off + PAGE_SIZE));
189 err = mapped;
190 goto ret;
191 }
192 origin = NULL;
193 }
194 /* Page mapping loop finished normally, nothing to clean up. */
195 clean = 0;
196
197ret:
198 if (clean > 0) {
199 /*
200 * Something went wrong. Clean up shadow/origin pages allocated
201 * on the last loop iteration, then delete mappings created
202 * during the previous iterations.
203 */
204 if (shadow)
205 __free_pages(page: shadow, order: 1);
206 if (origin)
207 __free_pages(page: origin, order: 1);
208 __vunmap_range_noflush(
209 start: vmalloc_shadow(addr: start),
210 end: vmalloc_shadow(addr: start + clean * PAGE_SIZE));
211 __vunmap_range_noflush(
212 start: vmalloc_origin(addr: start),
213 end: vmalloc_origin(addr: start + clean * PAGE_SIZE));
214 }
215 flush_cache_vmap(start: vmalloc_shadow(addr: start), end: vmalloc_shadow(addr: end));
216 flush_cache_vmap(start: vmalloc_origin(addr: start), end: vmalloc_origin(addr: end));
217 kmsan_leave_runtime();
218 return err;
219}
220
221void kmsan_iounmap_page_range(unsigned long start, unsigned long end)
222{
223 unsigned long v_shadow, v_origin;
224 struct page *shadow, *origin;
225 int nr;
226
227 if (!kmsan_enabled || kmsan_in_runtime())
228 return;
229
230 nr = (end - start) / PAGE_SIZE;
231 kmsan_enter_runtime();
232 v_shadow = (unsigned long)vmalloc_shadow(addr: start);
233 v_origin = (unsigned long)vmalloc_origin(addr: start);
234 for (int i = 0; i < nr;
235 i++, v_shadow += PAGE_SIZE, v_origin += PAGE_SIZE) {
236 shadow = kmsan_vmalloc_to_page_or_null(vaddr: (void *)v_shadow);
237 origin = kmsan_vmalloc_to_page_or_null(vaddr: (void *)v_origin);
238 __vunmap_range_noflush(start: v_shadow, end: vmalloc_shadow(addr: end));
239 __vunmap_range_noflush(start: v_origin, end: vmalloc_origin(addr: end));
240 if (shadow)
241 __free_pages(page: shadow, order: 1);
242 if (origin)
243 __free_pages(page: origin, order: 1);
244 }
245 flush_cache_vmap(start: vmalloc_shadow(addr: start), end: vmalloc_shadow(addr: end));
246 flush_cache_vmap(start: vmalloc_origin(addr: start), end: vmalloc_origin(addr: end));
247 kmsan_leave_runtime();
248}
249
250void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
251 size_t left)
252{
253 unsigned long ua_flags;
254
255 if (!kmsan_enabled || kmsan_in_runtime())
256 return;
257 /*
258 * At this point we've copied the memory already. It's hard to check it
259 * before copying, as the size of actually copied buffer is unknown.
260 */
261
262 /* copy_to_user() may copy zero bytes. No need to check. */
263 if (!to_copy)
264 return;
265 /* Or maybe copy_to_user() failed to copy anything. */
266 if (to_copy <= left)
267 return;
268
269 ua_flags = user_access_save();
270 if ((u64)to < TASK_SIZE) {
271 /* This is a user memory access, check it. */
272 kmsan_internal_check_memory(addr: (void *)from, size: to_copy - left, user_addr: to,
273 reason: REASON_COPY_TO_USER);
274 } else {
275 /* Otherwise this is a kernel memory access. This happens when a
276 * compat syscall passes an argument allocated on the kernel
277 * stack to a real syscall.
278 * Don't check anything, just copy the shadow of the copied
279 * bytes.
280 */
281 kmsan_internal_memmove_metadata(dst: (void *)to, src: (void *)from,
282 n: to_copy - left);
283 }
284 user_access_restore(ua_flags);
285}
286EXPORT_SYMBOL(kmsan_copy_to_user);
287
288/* Helper function to check an URB. */
289void kmsan_handle_urb(const struct urb *urb, bool is_out)
290{
291 if (!urb)
292 return;
293 if (is_out)
294 kmsan_internal_check_memory(addr: urb->transfer_buffer,
295 size: urb->transfer_buffer_length,
296 /*user_addr*/ 0, reason: REASON_SUBMIT_URB);
297 else
298 kmsan_internal_unpoison_memory(address: urb->transfer_buffer,
299 size: urb->transfer_buffer_length,
300 /*checked*/ false);
301}
302EXPORT_SYMBOL_GPL(kmsan_handle_urb);
303
304static void kmsan_handle_dma_page(const void *addr, size_t size,
305 enum dma_data_direction dir)
306{
307 switch (dir) {
308 case DMA_BIDIRECTIONAL:
309 kmsan_internal_check_memory(addr: (void *)addr, size, /*user_addr*/ 0,
310 reason: REASON_ANY);
311 kmsan_internal_unpoison_memory(address: (void *)addr, size,
312 /*checked*/ false);
313 break;
314 case DMA_TO_DEVICE:
315 kmsan_internal_check_memory(addr: (void *)addr, size, /*user_addr*/ 0,
316 reason: REASON_ANY);
317 break;
318 case DMA_FROM_DEVICE:
319 kmsan_internal_unpoison_memory(address: (void *)addr, size,
320 /*checked*/ false);
321 break;
322 case DMA_NONE:
323 break;
324 }
325}
326
327/* Helper function to handle DMA data transfers. */
328void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
329 enum dma_data_direction dir)
330{
331 u64 page_offset, to_go, addr;
332
333 if (PageHighMem(page))
334 return;
335 addr = (u64)page_address(page) + offset;
336 /*
337 * The kernel may occasionally give us adjacent DMA pages not belonging
338 * to the same allocation. Process them separately to avoid triggering
339 * internal KMSAN checks.
340 */
341 while (size > 0) {
342 page_offset = offset_in_page(addr);
343 to_go = min(PAGE_SIZE - page_offset, (u64)size);
344 kmsan_handle_dma_page(addr: (void *)addr, size: to_go, dir);
345 addr += to_go;
346 size -= to_go;
347 }
348}
349
350void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
351 enum dma_data_direction dir)
352{
353 struct scatterlist *item;
354 int i;
355
356 for_each_sg(sg, item, nents, i)
357 kmsan_handle_dma(sg_page(sg: item), item->offset, item->length,
358 dir);
359}
360
361/* Functions from kmsan-checks.h follow. */
362
363/*
364 * To create an origin, kmsan_poison_memory() unwinds the stacks and stores it
365 * into the stack depot. This may cause deadlocks if done from within KMSAN
366 * runtime, therefore we bail out if kmsan_in_runtime().
367 */
368void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)
369{
370 if (!kmsan_enabled || kmsan_in_runtime())
371 return;
372 kmsan_enter_runtime();
373 /* The users may want to poison/unpoison random memory. */
374 kmsan_internal_poison_memory(address: (void *)address, size, flags,
375 KMSAN_POISON_NOCHECK);
376 kmsan_leave_runtime();
377}
378EXPORT_SYMBOL(kmsan_poison_memory);
379
380/*
381 * Unlike kmsan_poison_memory(), this function can be used from within KMSAN
382 * runtime, because it does not trigger allocations or call instrumented code.
383 */
384void kmsan_unpoison_memory(const void *address, size_t size)
385{
386 unsigned long ua_flags;
387
388 if (!kmsan_enabled)
389 return;
390
391 ua_flags = user_access_save();
392 /* The users may want to poison/unpoison random memory. */
393 kmsan_internal_unpoison_memory(address: (void *)address, size,
394 KMSAN_POISON_NOCHECK);
395 user_access_restore(ua_flags);
396}
397EXPORT_SYMBOL(kmsan_unpoison_memory);
398
399/*
400 * Version of kmsan_unpoison_memory() called from IRQ entry functions.
401 */
402void kmsan_unpoison_entry_regs(const struct pt_regs *regs)
403{
404 kmsan_unpoison_memory((void *)regs, sizeof(*regs));
405}
406
407void kmsan_check_memory(const void *addr, size_t size)
408{
409 if (!kmsan_enabled)
410 return;
411 return kmsan_internal_check_memory(addr: (void *)addr, size, /*user_addr*/ 0,
412 reason: REASON_ANY);
413}
414EXPORT_SYMBOL(kmsan_check_memory);
415

source code of linux/mm/kmsan/hooks.c