mm/kmsan/hooks.c

   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
  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
  40 void 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
  50 void 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
  73 void 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
  94 void 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
 110 void 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
 126 static unsigned long vmalloc_shadow(unsigned long addr)
 127 {
 128         return (unsigned long)kmsan_get_metadata((void *)addr,
 129                                                  KMSAN_META_SHADOW);
 130 }
 131
 132 static unsigned long vmalloc_origin(unsigned long addr)
 133 {
 134         return (unsigned long)kmsan_get_metadata((void *)addr,
 135                                                  KMSAN_META_ORIGIN);
 136 }
 137
 138 void 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  */
 151 void 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
 182 void 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
 211 void 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 }
 247 EXPORT_SYMBOL(kmsan_copy_to_user);
 248
 249 /* Helper function to check an URB. */
 250 void 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 }
 263
 264 static void kmsan_handle_dma_page(const void *addr, size_t size,
 265                                   enum dma_data_direction dir)
 266 {
 267         switch (dir) {
 268         case DMA_BIDIRECTIONAL:
 269                 kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
 270                                             REASON_ANY);
 271                 kmsan_internal_unpoison_memory((void *)addr, size,
 272                                                /*checked*/ false);
 273                 break;
 274         case DMA_TO_DEVICE:
 275                 kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
 276                                             REASON_ANY);
 277                 break;
 278         case DMA_FROM_DEVICE:
 279                 kmsan_internal_unpoison_memory((void *)addr, size,
 280                                                /*checked*/ false);
 281                 break;
 282         case DMA_NONE:
 283                 break;
 284         }
 285 }
 286
 287 /* Helper function to handle DMA data transfers. */
 288 void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
 289                       enum dma_data_direction dir)
 290 {
 291         u64 page_offset, to_go, addr;
 292
 293         if (PageHighMem(page))
 294                 return;
 295         addr = (u64)page_address(page) + offset;
 296         /*
 297          * The kernel may occasionally give us adjacent DMA pages not belonging
 298          * to the same allocation. Process them separately to avoid triggering
 299          * internal KMSAN checks.
 300          */
 301         while (size > 0) {
 302                 page_offset = addr % PAGE_SIZE;
 303                 to_go = min(PAGE_SIZE - page_offset, (u64)size);
 304                 kmsan_handle_dma_page((void *)addr, to_go, dir);
 305                 addr += to_go;
 306                 size -= to_go;
 307         }
 308 }
 309
 310 void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
 311                          enum dma_data_direction dir)
 312 {
 313         struct scatterlist *item;
 314         int i;
 315
 316         for_each_sg(sg, item, nents, i)
 317                 kmsan_handle_dma(sg_page(item), item->offset, item->length,
 318                                  dir);
 319 }
 320
 321 /* Functions from kmsan-checks.h follow. */
 322 void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)
 323 {
 324         if (!kmsan_enabled || kmsan_in_runtime())
 325                 return;
 326         kmsan_enter_runtime();
 327         /* The users may want to poison/unpoison random memory. */
 328         kmsan_internal_poison_memory((void *)address, size, flags,
 329                                      KMSAN_POISON_NOCHECK);
 330         kmsan_leave_runtime();
 331 }
 332 EXPORT_SYMBOL(kmsan_poison_memory);
 333
 334 void kmsan_unpoison_memory(const void *address, size_t size)
 335 {
 336         unsigned long ua_flags;
 337
 338         if (!kmsan_enabled || kmsan_in_runtime())
 339                 return;
 340
 341         ua_flags = user_access_save();
 342         kmsan_enter_runtime();
 343         /* The users may want to poison/unpoison random memory. */
 344         kmsan_internal_unpoison_memory((void *)address, size,
 345                                        KMSAN_POISON_NOCHECK);
 346         kmsan_leave_runtime();
 347         user_access_restore(ua_flags);
 348 }
 349 EXPORT_SYMBOL(kmsan_unpoison_memory);
 350
 351 /*
 352  * Version of kmsan_unpoison_memory() that can be called from within the KMSAN
 353  * runtime.
 354  *
 355  * Non-instrumented IRQ entry functions receive struct pt_regs from assembly
 356  * code. Those regs need to be unpoisoned, otherwise using them will result in
 357  * false positives.
 358  * Using kmsan_unpoison_memory() is not an option in entry code, because the
 359  * return value of in_task() is inconsistent - as a result, certain calls to
 360  * kmsan_unpoison_memory() are ignored. kmsan_unpoison_entry_regs() ensures that
 361  * the registers are unpoisoned even if kmsan_in_runtime() is true in the early
 362  * entry code.
 363  */
 364 void kmsan_unpoison_entry_regs(const struct pt_regs *regs)
 365 {
 366         unsigned long ua_flags;
 367
 368         if (!kmsan_enabled)
 369                 return;
 370
 371         ua_flags = user_access_save();
 372         kmsan_internal_unpoison_memory((void *)regs, sizeof(*regs),
 373                                        KMSAN_POISON_NOCHECK);
 374         user_access_restore(ua_flags);
 375 }
 376
 377 void kmsan_check_memory(const void *addr, size_t size)
 378 {
 379         if (!kmsan_enabled)
 380                 return;
 381         return kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
 382                                            REASON_ANY);
 383 }
 384 EXPORT_SYMBOL(kmsan_check_memory);