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Subject: Re: BUG: memcmp(): Accessing invalid memory location
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Chandan Rajendra <chandan@linux.ibm.com>, linuxppc-dev@lists.ozlabs.org
Date: Fri, 25 Jan 2019 11:55:34 +1100
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Cc: Anton Blanchard <anton@au1.ibm.com>, Nick Piggin <npiggin@au1.ibm.com>,
 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
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On Thu, 2019-01-24 at 19:48 +0530, Chandan Rajendra wrote:
> - Here we execute "LD rB,0,r4". In the case of this bug, r4 has an unaligned
>   value and hence ends up accessing the "next" double word. The "next" double
>   word happens to occur after the last page mapped into the kernel's address
>   space and hence this leads to the previously listed oops.
>   

This is interesting ... should we mark the last page of any piece of
mapped linear mapping as reserved to avoid that sort of issue ?

Nick ? Aneesh ?

Cheers,
Ben.