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384 lines
11 KiB
384 lines
11 KiB
// 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 <[email protected]> |
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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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void 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; |
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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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for (int i = 0; i < nr; i++, off += PAGE_SIZE) { |
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shadow = alloc_pages(gfp_mask, 1); |
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origin = alloc_pages(gfp_mask, 1); |
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__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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__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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} |
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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_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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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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