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Date:   Thu, 2 Dec 2021 18:11:12 +0000
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Calvin Zhang <calvinzhang.cool@gmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH] mm: kmemleak: Ignore kmemleak scanning on CMA regions
Message-ID: <YakMQA1A75ZADeHi@arm.com>
References: <20211126024711.54937-1-calvinzhang.cool@gmail.com>
 <20211127160718.54e82aa93c977a367404a9e3@linux-foundation.org>
 <YaLgfYzxFRVamvdI@debian>
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On Sun, Nov 28, 2021 at 09:50:53AM +0800, Calvin Zhang wrote:
> On Sat, Nov 27, 2021 at 04:07:18PM -0800, Andrew Morton wrote:
> >On Fri, 26 Nov 2021 10:47:11 +0800 Calvin Zhang <calvinzhang.cool@gmail.com> wrote:
> >> Just like this:
> >> commit 620951e27457 ("mm/cma: make kmemleak ignore CMA regions").
> >> 
> >> Add kmemleak_ignore_phys() for CMA created from of reserved node.
[...]
> >The 620951e27457 changelog says "Without this, the kernel crashes...". 
> >Does your patch also fix a crash?  If so under what circumstances and
> >should we backport this fix into -stable kernels?
> 
> No crash occurred. 620951e27457 avoids crashes caused by accessing
> highmem and it was fixed later. Now kmemleak_alloc_phys() and
> kmemleak_ignore_phys() skip highmem. This patch is based on the
> point that CMA regions don't contain pointers to other kmemleak
> objects, and ignores CMA regions from reserved memory as what
> 620951e27457 did.

Note that kmemleak_ignore() only works if there was a prior
kmemleak_alloc() on that address range. With the previous commit we get
this via the memblock_alloc_range() but I fail to see one on the
rmem_cma_setup() path.

-- 
Catalin