[PATCH v3] mm: Defer kmemleak object creation of module_alloc()

[Kefeng Wang]

On 2021/11/25 5:50, Andrew Morton wrote:
> On Wed, 24 Nov 2021 22:20:34 +0800 Kefeng Wang <wangkefeng.wang at huawei.com> wrote:
>
>> Yongqiang reports a kmemleak panic when module insmod/rmmod
>> with KASAN enabled(without KASAN_VMALLOC) on x86[1].
>>
>> When the module area allocates memory, it's kmemleak_object
>> is created successfully, but the KASAN shadow memory of module
>> allocation is not ready, so when kmemleak scan the module's
>> pointer, it will panic due to no shadow memory with KASAN check.
>>
>> module_alloc
>>    __vmalloc_node_range
>>      kmemleak_vmalloc
>> 				kmemleak_scan
>> 				  update_checksum
>>    kasan_module_alloc
>>      kmemleak_ignore
>>
>> Note, there is no problem if KASAN_VMALLOC enabled, the modules
>> area entire shadow memory is preallocated. Thus, the bug only
>> exits on ARCH which supports dynamic allocation of module area
>> per module load, for now, only x86/arm64/s390 are involved.
>>
>> Add a VM_DEFER_KMEMLEAK flags, defer vmalloc'ed object register
>> of kmemleak in module_alloc() to fix this issue.
>>
> I guess this is worth backporting into -stable kernels?  If so, what
> would be a suitable Fixes: target?  I suspect it goes back to the
> initial KASAN merge date?

The kasan_module_alloc() was introduced from v4.0,

s390: v4.20

793213a82de4 s390/kasan: dynamic shadow mem allocation for modules

arm64: v4.4

39d114ddc682 arm64: add KASAN support

x86: v4.0

bebf56a1b176 kasan: enable instrumentation of global variables

> .