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
kmsan_task_create(struct task_struct * task)33 void kmsan_task_create(struct task_struct *task)
34 {
35 kmsan_enter_runtime();
36 kmsan_internal_task_create(task);
37 kmsan_leave_runtime();
38 }
39
kmsan_task_exit(struct task_struct * task)40 void kmsan_task_exit(struct task_struct *task)
41 {
42 if (!kmsan_enabled || kmsan_in_runtime())
43 return;
44
45 kmsan_disable_current();
46 }
47
kmsan_slab_alloc(struct kmem_cache * s,void * object,gfp_t flags)48 void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags)
49 {
50 if (unlikely(object == NULL))
51 return;
52 if (!kmsan_enabled || kmsan_in_runtime())
53 return;
54 /*
55 * There's a ctor or this is an RCU cache - do nothing. The memory
56 * status hasn't changed since last use.
57 */
58 if (s->ctor || (s->flags & SLAB_TYPESAFE_BY_RCU))
59 return;
60
61 kmsan_enter_runtime();
62 if (flags & __GFP_ZERO)
63 kmsan_internal_unpoison_memory(object, s->object_size,
64 KMSAN_POISON_CHECK);
65 else
66 kmsan_internal_poison_memory(object, s->object_size, flags,
67 KMSAN_POISON_CHECK);
68 kmsan_leave_runtime();
69 }
70
kmsan_slab_free(struct kmem_cache * s,void * object)71 void kmsan_slab_free(struct kmem_cache *s, void *object)
72 {
73 if (!kmsan_enabled || kmsan_in_runtime())
74 return;
75
76 /* RCU slabs could be legally used after free within the RCU period */
77 if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU))
78 return;
79 /*
80 * If there's a constructor, freed memory must remain in the same state
81 * until the next allocation. We cannot save its state to detect
82 * use-after-free bugs, instead we just keep it unpoisoned.
83 */
84 if (s->ctor)
85 return;
86 kmsan_enter_runtime();
87 kmsan_internal_poison_memory(object, s->object_size, GFP_KERNEL,
88 KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
89 kmsan_leave_runtime();
90 }
91
kmsan_kmalloc_large(const void * ptr,size_t size,gfp_t flags)92 void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
93 {
94 if (unlikely(ptr == NULL))
95 return;
96 if (!kmsan_enabled || kmsan_in_runtime())
97 return;
98 kmsan_enter_runtime();
99 if (flags & __GFP_ZERO)
100 kmsan_internal_unpoison_memory((void *)ptr, size,
101 /*checked*/ true);
102 else
103 kmsan_internal_poison_memory((void *)ptr, size, flags,
104 KMSAN_POISON_CHECK);
105 kmsan_leave_runtime();
106 }
107
kmsan_kfree_large(const void * ptr)108 void kmsan_kfree_large(const void *ptr)
109 {
110 struct page *page;
111
112 if (!kmsan_enabled || kmsan_in_runtime())
113 return;
114 kmsan_enter_runtime();
115 page = virt_to_head_page((void *)ptr);
116 KMSAN_WARN_ON(ptr != page_address(page));
117 kmsan_internal_poison_memory((void *)ptr, page_size(page), GFP_KERNEL,
118 KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
119 kmsan_leave_runtime();
120 }
121
vmalloc_shadow(unsigned long addr)122 static unsigned long vmalloc_shadow(unsigned long addr)
123 {
124 return (unsigned long)kmsan_get_metadata((void *)addr,
125 KMSAN_META_SHADOW);
126 }
127
vmalloc_origin(unsigned long addr)128 static unsigned long vmalloc_origin(unsigned long addr)
129 {
130 return (unsigned long)kmsan_get_metadata((void *)addr,
131 KMSAN_META_ORIGIN);
132 }
133
kmsan_vunmap_range_noflush(unsigned long start,unsigned long end)134 void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end)
135 {
136 __vunmap_range_noflush(vmalloc_shadow(start), vmalloc_shadow(end));
137 __vunmap_range_noflush(vmalloc_origin(start), vmalloc_origin(end));
138 flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
139 flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
140 }
141
142 /*
143 * This function creates new shadow/origin pages for the physical pages mapped
144 * into the virtual memory. If those physical pages already had shadow/origin,
145 * those are ignored.
146 */
kmsan_ioremap_page_range(unsigned long start,unsigned long end,phys_addr_t phys_addr,pgprot_t prot,unsigned int page_shift)147 int kmsan_ioremap_page_range(unsigned long start, unsigned long end,
148 phys_addr_t phys_addr, pgprot_t prot,
149 unsigned int page_shift)
150 {
151 gfp_t gfp_mask = GFP_KERNEL | __GFP_ZERO;
152 struct page *shadow, *origin;
153 unsigned long off = 0;
154 int nr, err = 0, clean = 0, mapped;
155
156 if (!kmsan_enabled || kmsan_in_runtime())
157 return 0;
158
159 nr = (end - start) / PAGE_SIZE;
160 kmsan_enter_runtime();
161 for (int i = 0; i < nr; i++, off += PAGE_SIZE, clean = i) {
162 shadow = alloc_pages(gfp_mask, 1);
163 origin = alloc_pages(gfp_mask, 1);
164 if (!shadow || !origin) {
165 err = -ENOMEM;
166 goto ret;
167 }
168 mapped = __vmap_pages_range_noflush(
169 vmalloc_shadow(start + off),
170 vmalloc_shadow(start + off + PAGE_SIZE), prot, &shadow,
171 PAGE_SHIFT);
172 if (mapped) {
173 err = mapped;
174 goto ret;
175 }
176 shadow = NULL;
177 mapped = __vmap_pages_range_noflush(
178 vmalloc_origin(start + off),
179 vmalloc_origin(start + off + PAGE_SIZE), prot, &origin,
180 PAGE_SHIFT);
181 if (mapped) {
182 __vunmap_range_noflush(
183 vmalloc_shadow(start + off),
184 vmalloc_shadow(start + off + PAGE_SIZE));
185 err = mapped;
186 goto ret;
187 }
188 origin = NULL;
189 }
190 /* Page mapping loop finished normally, nothing to clean up. */
191 clean = 0;
192
193 ret:
194 if (clean > 0) {
195 /*
196 * Something went wrong. Clean up shadow/origin pages allocated
197 * on the last loop iteration, then delete mappings created
198 * during the previous iterations.
199 */
200 if (shadow)
201 __free_pages(shadow, 1);
202 if (origin)
203 __free_pages(origin, 1);
204 __vunmap_range_noflush(
205 vmalloc_shadow(start),
206 vmalloc_shadow(start + clean * PAGE_SIZE));
207 __vunmap_range_noflush(
208 vmalloc_origin(start),
209 vmalloc_origin(start + clean * PAGE_SIZE));
210 }
211 flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
212 flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
213 kmsan_leave_runtime();
214 return err;
215 }
216
kmsan_iounmap_page_range(unsigned long start,unsigned long end)217 void kmsan_iounmap_page_range(unsigned long start, unsigned long end)
218 {
219 unsigned long v_shadow, v_origin;
220 struct page *shadow, *origin;
221 int nr;
222
223 if (!kmsan_enabled || kmsan_in_runtime())
224 return;
225
226 nr = (end - start) / PAGE_SIZE;
227 kmsan_enter_runtime();
228 v_shadow = (unsigned long)vmalloc_shadow(start);
229 v_origin = (unsigned long)vmalloc_origin(start);
230 for (int i = 0; i < nr;
231 i++, v_shadow += PAGE_SIZE, v_origin += PAGE_SIZE) {
232 shadow = kmsan_vmalloc_to_page_or_null((void *)v_shadow);
233 origin = kmsan_vmalloc_to_page_or_null((void *)v_origin);
234 __vunmap_range_noflush(v_shadow, vmalloc_shadow(end));
235 __vunmap_range_noflush(v_origin, vmalloc_origin(end));
236 if (shadow)
237 __free_pages(shadow, 1);
238 if (origin)
239 __free_pages(origin, 1);
240 }
241 flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
242 flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
243 kmsan_leave_runtime();
244 }
245
kmsan_copy_to_user(void __user * to,const void * from,size_t to_copy,size_t left)246 void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
247 size_t left)
248 {
249 unsigned long ua_flags;
250
251 if (!kmsan_enabled || kmsan_in_runtime())
252 return;
253 /*
254 * At this point we've copied the memory already. It's hard to check it
255 * before copying, as the size of actually copied buffer is unknown.
256 */
257
258 /* copy_to_user() may copy zero bytes. No need to check. */
259 if (!to_copy)
260 return;
261 /* Or maybe copy_to_user() failed to copy anything. */
262 if (to_copy <= left)
263 return;
264
265 ua_flags = user_access_save();
266 if (!IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) ||
267 (u64)to < TASK_SIZE) {
268 /* This is a user memory access, check it. */
269 kmsan_internal_check_memory((void *)from, to_copy - left, to,
270 REASON_COPY_TO_USER);
271 } else {
272 /* Otherwise this is a kernel memory access. This happens when a
273 * compat syscall passes an argument allocated on the kernel
274 * stack to a real syscall.
275 * Don't check anything, just copy the shadow of the copied
276 * bytes.
277 */
278 kmsan_enter_runtime();
279 kmsan_internal_memmove_metadata((void *)to, (void *)from,
280 to_copy - left);
281 kmsan_leave_runtime();
282 }
283 user_access_restore(ua_flags);
284 }
285 EXPORT_SYMBOL(kmsan_copy_to_user);
286
kmsan_memmove(void * to,const void * from,size_t size)287 void kmsan_memmove(void *to, const void *from, size_t size)
288 {
289 if (!kmsan_enabled || kmsan_in_runtime())
290 return;
291
292 kmsan_enter_runtime();
293 kmsan_internal_memmove_metadata(to, (void *)from, size);
294 kmsan_leave_runtime();
295 }
296 EXPORT_SYMBOL(kmsan_memmove);
297
298 /* Helper function to check an URB. */
kmsan_handle_urb(const struct urb * urb,bool is_out)299 void kmsan_handle_urb(const struct urb *urb, bool is_out)
300 {
301 if (!urb)
302 return;
303 if (is_out)
304 kmsan_internal_check_memory(urb->transfer_buffer,
305 urb->transfer_buffer_length,
306 /*user_addr*/ NULL,
307 REASON_SUBMIT_URB);
308 else
309 kmsan_internal_unpoison_memory(urb->transfer_buffer,
310 urb->transfer_buffer_length,
311 /*checked*/ false);
312 }
313 EXPORT_SYMBOL_GPL(kmsan_handle_urb);
314
kmsan_handle_dma_page(const void * addr,size_t size,enum dma_data_direction dir)315 static void kmsan_handle_dma_page(const void *addr, size_t size,
316 enum dma_data_direction dir)
317 {
318 switch (dir) {
319 case DMA_BIDIRECTIONAL:
320 kmsan_internal_check_memory((void *)addr, size,
321 /*user_addr*/ NULL, REASON_ANY);
322 kmsan_internal_unpoison_memory((void *)addr, size,
323 /*checked*/ false);
324 break;
325 case DMA_TO_DEVICE:
326 kmsan_internal_check_memory((void *)addr, size,
327 /*user_addr*/ NULL, REASON_ANY);
328 break;
329 case DMA_FROM_DEVICE:
330 kmsan_internal_unpoison_memory((void *)addr, size,
331 /*checked*/ false);
332 break;
333 case DMA_NONE:
334 break;
335 }
336 }
337
338 /* Helper function to handle DMA data transfers. */
kmsan_handle_dma(struct page * page,size_t offset,size_t size,enum dma_data_direction dir)339 void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
340 enum dma_data_direction dir)
341 {
342 u64 page_offset, to_go, addr;
343
344 if (PageHighMem(page))
345 return;
346 addr = (u64)page_address(page) + offset;
347 /*
348 * The kernel may occasionally give us adjacent DMA pages not belonging
349 * to the same allocation. Process them separately to avoid triggering
350 * internal KMSAN checks.
351 */
352 while (size > 0) {
353 page_offset = offset_in_page(addr);
354 to_go = min(PAGE_SIZE - page_offset, (u64)size);
355 kmsan_handle_dma_page((void *)addr, to_go, dir);
356 addr += to_go;
357 size -= to_go;
358 }
359 }
360 EXPORT_SYMBOL_GPL(kmsan_handle_dma);
361
kmsan_handle_dma_sg(struct scatterlist * sg,int nents,enum dma_data_direction dir)362 void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
363 enum dma_data_direction dir)
364 {
365 struct scatterlist *item;
366 int i;
367
368 for_each_sg(sg, item, nents, i)
369 kmsan_handle_dma(sg_page(item), item->offset, item->length,
370 dir);
371 }
372
373 /* Functions from kmsan-checks.h follow. */
374
375 /*
376 * To create an origin, kmsan_poison_memory() unwinds the stacks and stores it
377 * into the stack depot. This may cause deadlocks if done from within KMSAN
378 * runtime, therefore we bail out if kmsan_in_runtime().
379 */
kmsan_poison_memory(const void * address,size_t size,gfp_t flags)380 void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)
381 {
382 if (!kmsan_enabled || kmsan_in_runtime())
383 return;
384 kmsan_enter_runtime();
385 /* The users may want to poison/unpoison random memory. */
386 kmsan_internal_poison_memory((void *)address, size, flags,
387 KMSAN_POISON_NOCHECK);
388 kmsan_leave_runtime();
389 }
390 EXPORT_SYMBOL(kmsan_poison_memory);
391
392 /*
393 * Unlike kmsan_poison_memory(), this function can be used from within KMSAN
394 * runtime, because it does not trigger allocations or call instrumented code.
395 */
kmsan_unpoison_memory(const void * address,size_t size)396 void kmsan_unpoison_memory(const void *address, size_t size)
397 {
398 unsigned long ua_flags;
399
400 if (!kmsan_enabled)
401 return;
402
403 ua_flags = user_access_save();
404 /* The users may want to poison/unpoison random memory. */
405 kmsan_internal_unpoison_memory((void *)address, size,
406 KMSAN_POISON_NOCHECK);
407 user_access_restore(ua_flags);
408 }
409 EXPORT_SYMBOL(kmsan_unpoison_memory);
410
411 /*
412 * Version of kmsan_unpoison_memory() called from IRQ entry functions.
413 */
kmsan_unpoison_entry_regs(const struct pt_regs * regs)414 void kmsan_unpoison_entry_regs(const struct pt_regs *regs)
415 {
416 kmsan_unpoison_memory((void *)regs, sizeof(*regs));
417 }
418
kmsan_check_memory(const void * addr,size_t size)419 void kmsan_check_memory(const void *addr, size_t size)
420 {
421 if (!kmsan_enabled)
422 return;
423 return kmsan_internal_check_memory((void *)addr, size,
424 /*user_addr*/ NULL, REASON_ANY);
425 }
426 EXPORT_SYMBOL(kmsan_check_memory);
427
kmsan_enable_current(void)428 void kmsan_enable_current(void)
429 {
430 KMSAN_WARN_ON(current->kmsan_ctx.depth == 0);
431 current->kmsan_ctx.depth--;
432 }
433 EXPORT_SYMBOL(kmsan_enable_current);
434
kmsan_disable_current(void)435 void kmsan_disable_current(void)
436 {
437 current->kmsan_ctx.depth++;
438 KMSAN_WARN_ON(current->kmsan_ctx.depth == 0);
439 }
440 EXPORT_SYMBOL(kmsan_disable_current);
441