425 lines
12 KiB
C
425 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* KMSAN hooks for kernel subsystems.
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*
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* These functions handle creation of KMSAN metadata for memory allocations.
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*
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* Copyright (C) 2018-2022 Google LLC
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* Author: Alexander Potapenko <glider@google.com>
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*
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*/
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#include <linux/cacheflush.h>
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#include <linux/dma-direction.h>
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#include <linux/gfp.h>
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#include <linux/kmsan.h>
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#include <linux/mm.h>
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#include <linux/mm_types.h>
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#include <linux/scatterlist.h>
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#include <linux/slab.h>
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#include <linux/uaccess.h>
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#include <linux/usb.h>
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#include "../internal.h"
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#include "../slab.h"
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#include "kmsan.h"
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/*
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* Instrumented functions shouldn't be called under
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* kmsan_enter_runtime()/kmsan_leave_runtime(), because this will lead to
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* skipping effects of functions like memset() inside instrumented code.
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*/
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void kmsan_task_create(struct task_struct *task)
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{
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kmsan_enter_runtime();
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kmsan_internal_task_create(task);
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kmsan_leave_runtime();
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}
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void kmsan_task_exit(struct task_struct *task)
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{
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struct kmsan_ctx *ctx = &task->kmsan_ctx;
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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ctx->allow_reporting = false;
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}
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void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags)
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{
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if (unlikely(object == NULL))
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return;
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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/*
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* There's a ctor or this is an RCU cache - do nothing. The memory
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* status hasn't changed since last use.
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*/
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if (s->ctor || (s->flags & SLAB_TYPESAFE_BY_RCU))
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return;
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kmsan_enter_runtime();
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if (flags & __GFP_ZERO)
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kmsan_internal_unpoison_memory(object, s->object_size,
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KMSAN_POISON_CHECK);
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else
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kmsan_internal_poison_memory(object, s->object_size, flags,
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KMSAN_POISON_CHECK);
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kmsan_leave_runtime();
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}
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void kmsan_slab_free(struct kmem_cache *s, void *object)
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{
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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/* RCU slabs could be legally used after free within the RCU period */
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if (unlikely(s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)))
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return;
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/*
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* If there's a constructor, freed memory must remain in the same state
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* until the next allocation. We cannot save its state to detect
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* use-after-free bugs, instead we just keep it unpoisoned.
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*/
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if (s->ctor)
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return;
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kmsan_enter_runtime();
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kmsan_internal_poison_memory(object, s->object_size, GFP_KERNEL,
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KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
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kmsan_leave_runtime();
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}
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void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
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{
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if (unlikely(ptr == NULL))
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return;
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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kmsan_enter_runtime();
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if (flags & __GFP_ZERO)
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kmsan_internal_unpoison_memory((void *)ptr, size,
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/*checked*/ true);
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else
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kmsan_internal_poison_memory((void *)ptr, size, flags,
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KMSAN_POISON_CHECK);
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kmsan_leave_runtime();
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}
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void kmsan_kfree_large(const void *ptr)
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{
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struct page *page;
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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kmsan_enter_runtime();
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page = virt_to_head_page((void *)ptr);
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KMSAN_WARN_ON(ptr != page_address(page));
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kmsan_internal_poison_memory((void *)ptr,
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PAGE_SIZE << compound_order(page),
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GFP_KERNEL,
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KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
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kmsan_leave_runtime();
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}
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static unsigned long vmalloc_shadow(unsigned long addr)
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{
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return (unsigned long)kmsan_get_metadata((void *)addr,
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KMSAN_META_SHADOW);
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}
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static unsigned long vmalloc_origin(unsigned long addr)
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{
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return (unsigned long)kmsan_get_metadata((void *)addr,
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KMSAN_META_ORIGIN);
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}
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void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end)
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{
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__vunmap_range_noflush(vmalloc_shadow(start), vmalloc_shadow(end));
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__vunmap_range_noflush(vmalloc_origin(start), vmalloc_origin(end));
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flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
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flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
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}
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/*
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* This function creates new shadow/origin pages for the physical pages mapped
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* into the virtual memory. If those physical pages already had shadow/origin,
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* those are ignored.
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*/
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int kmsan_ioremap_page_range(unsigned long start, unsigned long end,
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phys_addr_t phys_addr, pgprot_t prot,
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unsigned int page_shift)
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{
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gfp_t gfp_mask = GFP_KERNEL | __GFP_ZERO;
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struct page *shadow, *origin;
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unsigned long off = 0;
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int nr, err = 0, clean = 0, mapped;
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if (!kmsan_enabled || kmsan_in_runtime())
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return 0;
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nr = (end - start) / PAGE_SIZE;
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kmsan_enter_runtime();
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for (int i = 0; i < nr; i++, off += PAGE_SIZE, clean = i) {
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shadow = alloc_pages(gfp_mask, 1);
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origin = alloc_pages(gfp_mask, 1);
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if (!shadow || !origin) {
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err = -ENOMEM;
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goto ret;
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}
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mapped = __vmap_pages_range_noflush(
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vmalloc_shadow(start + off),
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vmalloc_shadow(start + off + PAGE_SIZE), prot, &shadow,
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PAGE_SHIFT);
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if (mapped) {
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err = mapped;
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goto ret;
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}
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shadow = NULL;
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mapped = __vmap_pages_range_noflush(
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vmalloc_origin(start + off),
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vmalloc_origin(start + off + PAGE_SIZE), prot, &origin,
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PAGE_SHIFT);
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if (mapped) {
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__vunmap_range_noflush(
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vmalloc_shadow(start + off),
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vmalloc_shadow(start + off + PAGE_SIZE));
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err = mapped;
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goto ret;
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}
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origin = NULL;
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}
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/* Page mapping loop finished normally, nothing to clean up. */
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clean = 0;
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ret:
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if (clean > 0) {
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/*
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* Something went wrong. Clean up shadow/origin pages allocated
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* on the last loop iteration, then delete mappings created
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* during the previous iterations.
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*/
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if (shadow)
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__free_pages(shadow, 1);
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if (origin)
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__free_pages(origin, 1);
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__vunmap_range_noflush(
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vmalloc_shadow(start),
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vmalloc_shadow(start + clean * PAGE_SIZE));
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__vunmap_range_noflush(
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vmalloc_origin(start),
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vmalloc_origin(start + clean * PAGE_SIZE));
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}
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flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
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flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
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kmsan_leave_runtime();
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return err;
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}
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void kmsan_iounmap_page_range(unsigned long start, unsigned long end)
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{
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unsigned long v_shadow, v_origin;
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struct page *shadow, *origin;
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int nr;
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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nr = (end - start) / PAGE_SIZE;
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kmsan_enter_runtime();
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v_shadow = (unsigned long)vmalloc_shadow(start);
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v_origin = (unsigned long)vmalloc_origin(start);
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for (int i = 0; i < nr;
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i++, v_shadow += PAGE_SIZE, v_origin += PAGE_SIZE) {
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shadow = kmsan_vmalloc_to_page_or_null((void *)v_shadow);
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origin = kmsan_vmalloc_to_page_or_null((void *)v_origin);
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__vunmap_range_noflush(v_shadow, vmalloc_shadow(end));
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__vunmap_range_noflush(v_origin, vmalloc_origin(end));
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if (shadow)
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__free_pages(shadow, 1);
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if (origin)
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__free_pages(origin, 1);
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}
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flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
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flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
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kmsan_leave_runtime();
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}
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void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
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size_t left)
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{
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unsigned long ua_flags;
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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/*
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* At this point we've copied the memory already. It's hard to check it
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* before copying, as the size of actually copied buffer is unknown.
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*/
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/* copy_to_user() may copy zero bytes. No need to check. */
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if (!to_copy)
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return;
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/* Or maybe copy_to_user() failed to copy anything. */
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if (to_copy <= left)
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return;
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ua_flags = user_access_save();
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if ((u64)to < TASK_SIZE) {
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/* This is a user memory access, check it. */
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kmsan_internal_check_memory((void *)from, to_copy - left, to,
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REASON_COPY_TO_USER);
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} else {
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/* Otherwise this is a kernel memory access. This happens when a
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* compat syscall passes an argument allocated on the kernel
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* stack to a real syscall.
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* Don't check anything, just copy the shadow of the copied
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* bytes.
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*/
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kmsan_internal_memmove_metadata((void *)to, (void *)from,
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to_copy - left);
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}
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user_access_restore(ua_flags);
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}
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EXPORT_SYMBOL(kmsan_copy_to_user);
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/* Helper function to check an URB. */
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void kmsan_handle_urb(const struct urb *urb, bool is_out)
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{
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if (!urb)
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return;
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if (is_out)
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kmsan_internal_check_memory(urb->transfer_buffer,
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urb->transfer_buffer_length,
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/*user_addr*/ 0, REASON_SUBMIT_URB);
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else
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kmsan_internal_unpoison_memory(urb->transfer_buffer,
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urb->transfer_buffer_length,
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/*checked*/ false);
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}
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EXPORT_SYMBOL_GPL(kmsan_handle_urb);
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static void kmsan_handle_dma_page(const void *addr, size_t size,
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enum dma_data_direction dir)
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{
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switch (dir) {
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case DMA_BIDIRECTIONAL:
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kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
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REASON_ANY);
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kmsan_internal_unpoison_memory((void *)addr, size,
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/*checked*/ false);
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break;
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case DMA_TO_DEVICE:
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kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
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REASON_ANY);
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break;
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case DMA_FROM_DEVICE:
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kmsan_internal_unpoison_memory((void *)addr, size,
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/*checked*/ false);
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break;
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case DMA_NONE:
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break;
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}
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}
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/* Helper function to handle DMA data transfers. */
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void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
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enum dma_data_direction dir)
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{
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u64 page_offset, to_go, addr;
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if (PageHighMem(page))
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return;
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addr = (u64)page_address(page) + offset;
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/*
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* The kernel may occasionally give us adjacent DMA pages not belonging
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* to the same allocation. Process them separately to avoid triggering
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* internal KMSAN checks.
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*/
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while (size > 0) {
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page_offset = addr % PAGE_SIZE;
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to_go = min(PAGE_SIZE - page_offset, (u64)size);
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kmsan_handle_dma_page((void *)addr, to_go, dir);
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addr += to_go;
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size -= to_go;
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}
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}
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void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
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enum dma_data_direction dir)
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{
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struct scatterlist *item;
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int i;
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for_each_sg(sg, item, nents, i)
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kmsan_handle_dma(sg_page(item), item->offset, item->length,
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dir);
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}
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/* Functions from kmsan-checks.h follow. */
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void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)
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{
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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kmsan_enter_runtime();
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/* The users may want to poison/unpoison random memory. */
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kmsan_internal_poison_memory((void *)address, size, flags,
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KMSAN_POISON_NOCHECK);
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kmsan_leave_runtime();
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}
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EXPORT_SYMBOL(kmsan_poison_memory);
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void kmsan_unpoison_memory(const void *address, size_t size)
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{
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unsigned long ua_flags;
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if (!kmsan_enabled || kmsan_in_runtime())
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return;
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ua_flags = user_access_save();
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kmsan_enter_runtime();
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/* The users may want to poison/unpoison random memory. */
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kmsan_internal_unpoison_memory((void *)address, size,
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KMSAN_POISON_NOCHECK);
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kmsan_leave_runtime();
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user_access_restore(ua_flags);
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}
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EXPORT_SYMBOL(kmsan_unpoison_memory);
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/*
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* Version of kmsan_unpoison_memory() that can be called from within the KMSAN
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* runtime.
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*
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* Non-instrumented IRQ entry functions receive struct pt_regs from assembly
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* code. Those regs need to be unpoisoned, otherwise using them will result in
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* false positives.
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* Using kmsan_unpoison_memory() is not an option in entry code, because the
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* return value of in_task() is inconsistent - as a result, certain calls to
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* kmsan_unpoison_memory() are ignored. kmsan_unpoison_entry_regs() ensures that
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* the registers are unpoisoned even if kmsan_in_runtime() is true in the early
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* entry code.
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*/
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void kmsan_unpoison_entry_regs(const struct pt_regs *regs)
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{
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unsigned long ua_flags;
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if (!kmsan_enabled)
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return;
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ua_flags = user_access_save();
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kmsan_internal_unpoison_memory((void *)regs, sizeof(*regs),
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KMSAN_POISON_NOCHECK);
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user_access_restore(ua_flags);
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}
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void kmsan_check_memory(const void *addr, size_t size)
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{
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if (!kmsan_enabled)
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return;
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return kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
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REASON_ANY);
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}
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EXPORT_SYMBOL(kmsan_check_memory);
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