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