From 1e8e18f694a52d703665012ca486826f64bac29d Mon Sep 17 00:00:00 2001
From: Zhen Lei <thunder.leizhen@huawei.com>
Date: Tue, 3 Jul 2018 17:02:46 -0700
Subject: [PATCH] kasan: fix shadow_size calculation error in kasan_module_alloc
Git-commit: 1e8e18f694a52d703665012ca486826f64bac29d
Patch-mainline: v4.18-rc4
References: bsc#1051510
There is a special case that the size is "(N << KASAN_SHADOW_SCALE_SHIFT)
Pages plus X", the value of X is [1, KASAN_SHADOW_SCALE_SIZE-1]. The
operation "size >> KASAN_SHADOW_SCALE_SHIFT" will drop X, and the
roundup operation can not retrieve the missed one page. For example:
size=0x28006, PAGE_SIZE=0x1000, KASAN_SHADOW_SCALE_SHIFT=3, we will get
shadow_size=0x5000, but actually we need 6 pages.
shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT, PAGE_SIZE);
This can lead to a kernel crash when kasan is enabled and the value of
mod->core_layout.size or mod->init_layout.size is like above. Because
the shadow memory of X has not been allocated and mapped.
Move_module: ptr = module_alloc(mod->core_layout.size); ... memset(ptr, 0, mod->core_layout.size); //crashed
Unable to handle kernel paging request at virtual address ffff0fffff97b000
......
Call trace:
__asan_storeN+0x174/0x1a8
memset+0x24/0x48
layout_and_allocate+0xcd8/0x1800
load_module+0x190/0x23e8
SyS_finit_module+0x148/0x180
Link: http://lkml.kernel.org/r/1529659626-12660-1-git-send-email-thunder.leizhen@huawei.com
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Dmitriy Vyukov <dvyukov@google.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Libin <huawei.libin@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
mm/kasan/kasan.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index f185455b3406..c3bd5209da38 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -619,12 +619,13 @@ void kasan_kfree_large(void *ptr, unsigned long ip)
int kasan_module_alloc(void *addr, size_t size)
{
void *ret;
+ size_t scaled_size;
size_t shadow_size;
unsigned long shadow_start;
shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
- shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
- PAGE_SIZE);
+ scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
+ shadow_size = round_up(scaled_size, PAGE_SIZE);
if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
return -EINVAL;
--
2.16.4