linux-kernel - Re: [PATCH v3] mm: Defer kmemleak object creation of module

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Message-Id: <20211124135014.665649a0bcb872367b248cef@linux-foundation.org>
Date:   Wed, 24 Nov 2021 13:50:14 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-s390@...r.kernel.org>,
        <kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Alexander Potapenko <glider@...gle.com>,
        Yongqiang Liu <liuyongqiang13@...wei.com>
Subject: Re: [PATCH v3] mm: Defer kmemleak object creation of module_alloc()

On Wed, 24 Nov 2021 22:20:34 +0800 Kefeng Wang <wangkefeng.wang@...wei.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?