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

[Andrew Morton]

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?