linux-kernel - Re: [PATCH] MIPS: Fix HIGHMEM crash in __update

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Date:	Fri, 10 Apr 2015 16:31:06 +0200
From:	Lars Persson <lars.persson@...s.com>
To:	Ralf Baechle <ralf@...ux-mips.org>
CC:	Lars Persson <larper@...s.com>,
	"paul.burton@...tec.com" <paul.burton@...tec.com>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] MIPS: Fix HIGHMEM crash in __update_cache().

Ralf,

I came to think that also non-executable mappings for highmem pages could reach the flushing code in __update_cache() and trigger an OOPS.

Until the highmem patches are merged we should block highmem pages in __update_cache().  Could you add this to the patch ?

Sent from my iPhone

> 10 apr 2015 kl. 15:47 skrev Ralf Baechle <ralf@...ux-mips.org>:
> 
>> On Fri, Apr 10, 2015 at 03:21:24PM +0200, Lars Persson wrote:
>> 
>> Commit 8b5fe5e54b47 ("MIPS: Fix race condition in lazy cache flushing.")
>> triggered NULL pointer dereferences on systems with HIGHMEM.
>> 
>> The problem was caused by not clearing the PG_dcache_dirty flag in
>> flush_icache_page() and thus we enter __update_cache() that lacks
>> support for HIGHMEM.
> 
> Thanks, I've folded this patch into the original 8b5fe5e54b47 commit.
> 
>  Ralf
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