In kasan_init_region, when k_start is not page aligned,
at the begin of for loop, k_cur = k_start & PAGE_MASK
is less than k_start, and then va = block + k_cur - k_start
is less than block, the addr va is invalid, because the
memory address space from va to block is not alloced by
memblock_alloc, which will not be reserved
by memblock_reserve later, it will be used by other places.
As a result, memory overwriting occurs.
for example:
int __init __weak kasan_init_region(void *start, size_t size)
{
[...]
/* if say block(dcd97000) k_start(feef7400) k_end(feeff3fe) */
block = memblock_alloc(k_end - k_start, PAGE_SIZE);
[...]
for (k_cur = k_start & PAGE_MASK; k_cur < k_end; k_cur += PAGE_SIZE) {
/* at the begin of for loop
* block(dcd97000) va(dcd96c00) k_cur(feef7000)
k_start(feef7400)
* va(dcd96c00) is less than block(dcd97000), va is invalid
*/
void *va = block + k_cur - k_start;
[...]
}
[...]
}
Therefore, page alignment is performed on k_start before
memblock_alloc to ensure the validity of the VA address.
Fixes: 663c0c9496a6 ("powerpc/kasan: Fix shadow area set up for modules.")
Signed-off-by: Jiangfeng Xiao <xiaojiangf...@huawei.com>
---
arch/powerpc/mm/kasan/init_32.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/mm/kasan/init_32.c b/arch/powerpc/mm/kasan/init_32.c
index a70828a..aa9aa11 100644
--- a/arch/powerpc/mm/kasan/init_32.c
+++ b/arch/powerpc/mm/kasan/init_32.c
@@ -64,6 +64,7 @@ int __init __weak kasan_init_region(void *start, size_t size)
if (ret)
return ret;
+ k_start = k_start & PAGE_MASK;
block = memblock_alloc(k_end - k_start, PAGE_SIZE);
if (!block)
return -ENOMEM;
--
1.8.5.6
