linux-kernel - Re: [PATCH] powerpc/603: fix handling of the DIRTY flag

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Message-Id: <46DlGv5YRdz9sPl@ozlabs.org>
Date:   Thu, 22 Aug 2019 23:09:11 +1000 (AEST)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Doug Crawford <doug.crawford@...elight-its.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/603: fix handling of the DIRTY flag

On Mon, 2019-08-19 at 06:40:25 UTC, Christophe Leroy wrote:
> If a page is already mapped RW without the DIRTY flag, the DIRTY
> flag is never set and a TLB store miss exception is taken forever.
> 
> This is easily reproduced with the following app:
> 
> void main(void)
> {
> 	volatile char *ptr = mmap(0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
> 
> 	*ptr = *ptr;
> }
> 
> When DIRTY flag is not set, bail out of TLB miss handler and take
> a minor page fault which will set the DIRTY flag.
> 
> Fixes: f8b58c64eaef ("powerpc/603: let's handle PAGE_DIRTY directly")
> Cc: stable@...r.kernel.org
> Reported-by: Doug Crawford <doug.crawford@...elight-its.com>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/415480dce2ef03bb8335deebd2f402f475443ce0

cheers