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kmsan_hooks.c
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/
kmsan_hooks.c
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// SPDX-License-Identifier: GPL-2.0
/*
* KMSAN hooks for kernel subsystems.
*
* These functions handle creation of KMSAN metadata for memory allocations.
*
* Copyright (C) 2018-2019 Google LLC
* Author: Alexander Potapenko <glider@google.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <asm/cacheflush.h>
#include <linux/gfp.h>
#include <linux/i2c.h>
#include <linux/mm.h>
#include <linux/mm_types.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include "../slab.h"
#include "kmsan.h"
/* TODO(glider): do we need to export these symbols? */
/*
* The functions may call back to instrumented code, which, in turn, may call
* these hooks again. To avoid re-entrancy, we use __GFP_NO_KMSAN_SHADOW.
* Instrumented functions shouldn't be called under
* ENTER_RUNTIME()/LEAVE_RUNTIME(), because this will lead to skipping
* effects of functions like memset() inside instrumented code.
*/
/* Called from kernel/kthread.c, kernel/fork.c */
void kmsan_task_create(struct task_struct *task)
{
unsigned long irq_flags;
if (!task)
return;
ENTER_RUNTIME(irq_flags);
kmsan_internal_task_create(task);
LEAVE_RUNTIME(irq_flags);
}
EXPORT_SYMBOL(kmsan_task_create);
/* Called from kernel/exit.c */
void kmsan_task_exit(struct task_struct *task)
{
unsigned long irq_flags;
struct kmsan_task_state *state = &task->kmsan;
if (!kmsan_ready || IN_RUNTIME())
return;
ENTER_RUNTIME(irq_flags);
state->allow_reporting = false;
LEAVE_RUNTIME(irq_flags);
}
EXPORT_SYMBOL(kmsan_task_exit);
/* Called from mm/slub.c */
void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags)
{
unsigned long irq_flags;
if (unlikely(object == NULL))
return;
if (!kmsan_ready || 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;
ENTER_RUNTIME(irq_flags);
if (flags & __GFP_ZERO) {
kmsan_internal_unpoison_shadow(object, s->object_size,
KMSAN_POISON_CHECK);
} else {
kmsan_internal_poison_shadow(object, s->object_size, flags,
KMSAN_POISON_CHECK);
}
LEAVE_RUNTIME(irq_flags);
}
/* Called from mm/slub.c */
void kmsan_slab_free(struct kmem_cache *s, void *object)
{
unsigned long irq_flags;
if (!kmsan_ready || IN_RUNTIME())
return;
ENTER_RUNTIME(irq_flags);
/* RCU slabs could be legally used after free within the RCU period */
if (unlikely(s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)))
goto leave;
if (s->ctor)
goto leave;
kmsan_internal_poison_shadow(object, s->object_size,
GFP_KERNEL,
KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
leave:
LEAVE_RUNTIME(irq_flags);
}
/* Called from mm/slub.c */
void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
{
unsigned long irq_flags;
if (unlikely(ptr == NULL))
return;
if (!kmsan_ready || IN_RUNTIME())
return;
ENTER_RUNTIME(irq_flags);
if (flags & __GFP_ZERO) {
kmsan_internal_unpoison_shadow((void *)ptr, size,
/*checked*/true);
} else {
kmsan_internal_poison_shadow((void *)ptr, size, flags,
KMSAN_POISON_CHECK);
}
LEAVE_RUNTIME(irq_flags);
}
/* Called from mm/slub.c */
void kmsan_kfree_large(const void *ptr)
{
struct page *page;
unsigned long irq_flags;
if (!kmsan_ready || IN_RUNTIME())
return;
ENTER_RUNTIME(irq_flags);
page = virt_to_head_page((void *)ptr);
BUG_ON(ptr != page_address(page));
kmsan_internal_poison_shadow(
(void *)ptr, PAGE_SIZE << compound_order(page), GFP_KERNEL,
KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
LEAVE_RUNTIME(irq_flags);
}
static unsigned long vmalloc_shadow(unsigned long addr)
{
return (unsigned long)kmsan_get_metadata((void *)addr, 1, META_SHADOW);
}
static unsigned long vmalloc_origin(unsigned long addr)
{
return (unsigned long)kmsan_get_metadata((void *)addr, 1, META_ORIGIN);
}
/* Called from mm/vmalloc.c */
void kmsan_vunmap_page_range(unsigned long start, unsigned long end)
{
__vunmap_page_range(vmalloc_shadow(start), vmalloc_shadow(end));
__vunmap_page_range(vmalloc_origin(start), vmalloc_origin(end));
}
/* Called from lib/ioremap.c */
/*
* 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.
*/
void kmsan_ioremap_page_range(unsigned long start, unsigned long end,
phys_addr_t phys_addr, pgprot_t prot)
{
unsigned long irq_flags;
struct page *shadow, *origin;
int i, nr;
unsigned long off = 0;
gfp_t gfp_mask = GFP_KERNEL | __GFP_ZERO | __GFP_NO_KMSAN_SHADOW;
if (!kmsan_ready || IN_RUNTIME())
return;
nr = (end - start) / PAGE_SIZE;
ENTER_RUNTIME(irq_flags);
for (i = 0; i < nr; i++, off += PAGE_SIZE) {
shadow = alloc_pages(gfp_mask, 1);
origin = alloc_pages(gfp_mask, 1);
__vmap_page_range_noflush(vmalloc_shadow(start + off),
vmalloc_shadow(start + off + PAGE_SIZE),
prot, &shadow);
__vmap_page_range_noflush(vmalloc_origin(start + off),
vmalloc_origin(start + off + PAGE_SIZE),
prot, &origin);
}
flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
LEAVE_RUNTIME(irq_flags);
}
void kmsan_iounmap_page_range(unsigned long start, unsigned long end)
{
int i, nr;
struct page *shadow, *origin;
unsigned long v_shadow, v_origin;
unsigned long irq_flags;
if (!kmsan_ready || IN_RUNTIME())
return;
nr = (end - start) / PAGE_SIZE;
ENTER_RUNTIME(irq_flags);
v_shadow = (unsigned long)vmalloc_shadow(start);
v_origin = (unsigned long)vmalloc_origin(start);
for (i = 0; i < nr; i++, v_shadow += PAGE_SIZE, v_origin += PAGE_SIZE) {
shadow = vmalloc_to_page_or_null((void *)v_shadow);
origin = vmalloc_to_page_or_null((void *)v_origin);
__vunmap_page_range(v_shadow, v_shadow + PAGE_SIZE);
__vunmap_page_range(v_origin, v_origin + PAGE_SIZE);
if (shadow)
__free_pages(shadow, 1);
if (origin)
__free_pages(origin, 1);
}
LEAVE_RUNTIME(irq_flags);
}
/* Called from include/linux/uaccess.h, include/linux/uaccess.h */
void kmsan_copy_to_user(const void *to, const void *from,
size_t to_copy, size_t left)
{
void *shadow;
if (!kmsan_ready || 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;
if ((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);
return;
}
/* 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.
*/
shadow = kmsan_get_metadata((void *)to, to_copy - left, META_SHADOW);
if (shadow)
kmsan_memcpy_metadata((void *)to, (void *)from, to_copy - left);
}
EXPORT_SYMBOL(kmsan_copy_to_user);
void kmsan_poison_shadow(const void *address, size_t size, gfp_t flags)
{
unsigned long irq_flags;
if (!kmsan_ready || IN_RUNTIME())
return;
ENTER_RUNTIME(irq_flags);
/* The users may want to poison/unpoison random memory. */
kmsan_internal_poison_shadow((void *)address, size, flags,
KMSAN_POISON_NOCHECK);
LEAVE_RUNTIME(irq_flags);
}
EXPORT_SYMBOL(kmsan_poison_shadow);
void kmsan_unpoison_shadow(const void *address, size_t size)
{
unsigned long irq_flags;
if (!kmsan_ready || IN_RUNTIME())
return;
ENTER_RUNTIME(irq_flags);
/* The users may want to poison/unpoison random memory. */
kmsan_internal_unpoison_shadow((void *)address, size,
KMSAN_POISON_NOCHECK);
LEAVE_RUNTIME(irq_flags);
}
EXPORT_SYMBOL(kmsan_unpoison_shadow);
void kmsan_check_memory(const void *addr, size_t size)
{
return kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
REASON_ANY);
}
EXPORT_SYMBOL(kmsan_check_memory);
void kmsan_gup_pgd_range(struct page **pages, int nr)
{
int i;
void *page_addr;
/*
* gup_pgd_range() has just created a number of new pages that KMSAN
* treats as uninitialized. In the case they belong to the userspace
* memory, unpoison the corresponding kernel pages.
*/
for (i = 0; i < nr; i++) {
page_addr = page_address(pages[i]);
if (((u64)page_addr < TASK_SIZE) &&
((u64)page_addr + PAGE_SIZE < TASK_SIZE))
kmsan_unpoison_shadow(page_addr, PAGE_SIZE);
}
}
EXPORT_SYMBOL(kmsan_gup_pgd_range);
/* Helper function to check an SKB. */
void kmsan_check_skb(const struct sk_buff *skb)
{
int start = skb_headlen(skb);
struct sk_buff *frag_iter;
int i, copy = 0;
skb_frag_t *f;
u32 p_off, p_len, copied;
struct page *p;
u8 *vaddr;
if (!skb || !skb->len)
return;
kmsan_internal_check_memory(skb->data, skb_headlen(skb), 0, REASON_ANY);
if (skb_is_nonlinear(skb)) {
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
f = &skb_shinfo(skb)->frags[i];
skb_frag_foreach_page(f,
skb_frag_off(f) - start,
copy, p, p_off, p_len, copied) {
vaddr = kmap_atomic(p);
kmsan_internal_check_memory(vaddr + p_off,
p_len, /*user_addr*/ 0,
REASON_ANY);
kunmap_atomic(vaddr);
}
}
}
skb_walk_frags(skb, frag_iter)
kmsan_check_skb(frag_iter);
}
EXPORT_SYMBOL(kmsan_check_skb);
/* 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*/ 0, REASON_SUBMIT_URB);
else
kmsan_internal_unpoison_shadow(urb->transfer_buffer,
urb->transfer_buffer_length,
/*checked*/false);
}
EXPORT_SYMBOL(kmsan_handle_urb);
/* Helper function to check I2C-transferred data. */
void kmsan_handle_i2c_transfer(struct i2c_msg *msgs, int num)
{
int i;
if (!msgs)
return;
for (i = 0; i < num; i++) {
if (msgs[i].flags & I2C_M_RD)
kmsan_internal_unpoison_shadow(msgs[i].buf,
msgs[i].len,
/*checked*/false);
else
kmsan_internal_check_memory(msgs[i].buf, msgs[i].len,
/*user_addr*/0,
REASON_ANY);
}
}