Re: [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@xxxxxxxxxx> 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

> .