linux-kernel - Re: devm_memremap_pages() triggers a kasan_add_zero

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Date:   Fri, 16 Aug 2019 14:48:11 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Qian Cai <cai@....pw>
Cc:     Linux MM <linux-mm@...ck.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev@...glegroups.com
Subject: Re: devm_memremap_pages() triggers a kasan_add_zero_shadow() warning

On Fri, Aug 16, 2019 at 2:36 PM Qian Cai <cai@....pw> wrote:
>
> Every so often recently, booting Intel CPU server on linux-next triggers this
> warning. Trying to figure out if  the commit 7cc7867fb061
> ("mm/devm_memremap_pages: enable sub-section remap") is the culprit here.
>
> # ./scripts/faddr2line vmlinux devm_memremap_pages+0x894/0xc70
> devm_memremap_pages+0x894/0xc70:
> devm_memremap_pages at mm/memremap.c:307

Previously the forced section alignment in devm_memremap_pages() would
cause the implementation to never violate the KASAN_SHADOW_SCALE_SIZE
(12K on x86) constraint.

Can you provide a dump of /proc/iomem? I'm curious what resource is
triggering such a small alignment granularity.

Is it truly only linux-next or does latest mainline have this issue as well?