mirror of
https://github.com/torvalds/linux.git
synced 2025-10-31 16:48:26 +02:00
4117992df6
KASAN does not play well with the page poisoning (CONFIG_PAGE_POISONING). It triggers false positives in the allocation path: BUG: KASAN: use-after-free in memchr_inv+0x2ea/0x330 Read of size 8 at addr ffff88881f800000 by task swapper/0 CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc1+ #54 Call Trace: dump_stack+0xe0/0x19a print_address_description.cold.2+0x9/0x28b kasan_report.cold.3+0x7a/0xb5 __asan_report_load8_noabort+0x19/0x20 memchr_inv+0x2ea/0x330 kernel_poison_pages+0x103/0x3d5 get_page_from_freelist+0x15e7/0x4d90 because KASAN has not yet unpoisoned the shadow page for allocation before it checks memchr_inv() but only found a stale poison pattern. Also, false positives in free path, BUG: KASAN: slab-out-of-bounds in kernel_poison_pages+0x29e/0x3d5 Write of size 4096 at addr ffff8888112cc000 by task swapper/0/1 CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc1+ #55 Call Trace: dump_stack+0xe0/0x19a print_address_description.cold.2+0x9/0x28b kasan_report.cold.3+0x7a/0xb5 check_memory_region+0x22d/0x250 memset+0x28/0x40 kernel_poison_pages+0x29e/0x3d5 __free_pages_ok+0x75f/0x13e0 due to KASAN adds poisoned redzones around slab objects, but the page poisoning needs to poison the whole page. Link: http://lkml.kernel.org/r/20190114233405.67843-1-cai@lca.pw Signed-off-by: Qian Cai <cai@lca.pw> Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
134 lines
3 KiB
C
134 lines
3 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
#include <linux/kernel.h>
|
|
#include <linux/string.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/highmem.h>
|
|
#include <linux/page_ext.h>
|
|
#include <linux/poison.h>
|
|
#include <linux/ratelimit.h>
|
|
#include <linux/kasan.h>
|
|
|
|
static bool want_page_poisoning __read_mostly;
|
|
|
|
static int __init early_page_poison_param(char *buf)
|
|
{
|
|
if (!buf)
|
|
return -EINVAL;
|
|
return strtobool(buf, &want_page_poisoning);
|
|
}
|
|
early_param("page_poison", early_page_poison_param);
|
|
|
|
/**
|
|
* page_poisoning_enabled - check if page poisoning is enabled
|
|
*
|
|
* Return true if page poisoning is enabled, or false if not.
|
|
*/
|
|
bool page_poisoning_enabled(void)
|
|
{
|
|
/*
|
|
* Assumes that debug_pagealloc_enabled is set before
|
|
* memblock_free_all.
|
|
* Page poisoning is debug page alloc for some arches. If
|
|
* either of those options are enabled, enable poisoning.
|
|
*/
|
|
return (want_page_poisoning ||
|
|
(!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
|
|
debug_pagealloc_enabled()));
|
|
}
|
|
EXPORT_SYMBOL_GPL(page_poisoning_enabled);
|
|
|
|
static void poison_page(struct page *page)
|
|
{
|
|
void *addr = kmap_atomic(page);
|
|
|
|
/* KASAN still think the page is in-use, so skip it. */
|
|
kasan_disable_current();
|
|
memset(addr, PAGE_POISON, PAGE_SIZE);
|
|
kasan_enable_current();
|
|
kunmap_atomic(addr);
|
|
}
|
|
|
|
static void poison_pages(struct page *page, int n)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < n; i++)
|
|
poison_page(page + i);
|
|
}
|
|
|
|
static bool single_bit_flip(unsigned char a, unsigned char b)
|
|
{
|
|
unsigned char error = a ^ b;
|
|
|
|
return error && !(error & (error - 1));
|
|
}
|
|
|
|
static void check_poison_mem(unsigned char *mem, size_t bytes)
|
|
{
|
|
static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
|
|
unsigned char *start;
|
|
unsigned char *end;
|
|
|
|
if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
|
|
return;
|
|
|
|
start = memchr_inv(mem, PAGE_POISON, bytes);
|
|
if (!start)
|
|
return;
|
|
|
|
for (end = mem + bytes - 1; end > start; end--) {
|
|
if (*end != PAGE_POISON)
|
|
break;
|
|
}
|
|
|
|
if (!__ratelimit(&ratelimit))
|
|
return;
|
|
else if (start == end && single_bit_flip(*start, PAGE_POISON))
|
|
pr_err("pagealloc: single bit error\n");
|
|
else
|
|
pr_err("pagealloc: memory corruption\n");
|
|
|
|
print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
|
|
end - start + 1, 1);
|
|
dump_stack();
|
|
}
|
|
|
|
static void unpoison_page(struct page *page)
|
|
{
|
|
void *addr;
|
|
|
|
addr = kmap_atomic(page);
|
|
/*
|
|
* Page poisoning when enabled poisons each and every page
|
|
* that is freed to buddy. Thus no extra check is done to
|
|
* see if a page was posioned.
|
|
*/
|
|
check_poison_mem(addr, PAGE_SIZE);
|
|
kunmap_atomic(addr);
|
|
}
|
|
|
|
static void unpoison_pages(struct page *page, int n)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < n; i++)
|
|
unpoison_page(page + i);
|
|
}
|
|
|
|
void kernel_poison_pages(struct page *page, int numpages, int enable)
|
|
{
|
|
if (!page_poisoning_enabled())
|
|
return;
|
|
|
|
if (enable)
|
|
unpoison_pages(page, numpages);
|
|
else
|
|
poison_pages(page, numpages);
|
|
}
|
|
|
|
#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
|
|
void __kernel_map_pages(struct page *page, int numpages, int enable)
|
|
{
|
|
/* This function does nothing, all work is done via poison pages */
|
|
}
|
|
#endif
|