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In-Reply-To: <1452527374-4886-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
 benh@kernel.crashing.org, paulus@samba.org, Hugh Dickins <hughd@google.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 Laurent Dufour <ldufour@linux.vnet.ibm.com>
From: Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: [V2] mm/powerpc: Fix _PAGE_PTE breaking swapoff
Message-Id: <20160112123248.B9056140B96@ozlabs.org>
Date: Tue, 12 Jan 2016 23:32:48 +1100 (AEDT)
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On Mon, 2016-11-01 at 15:49:34 UTC, "Aneesh Kumar K.V" wrote:
> Core kernel expect swp_entry_t to be consisting of
> only swap type and swap offset. We should not leak pte bits to
> swp_entry_t. This breaks swapoff which use the swap type and offset
> to build a swp_entry_t and later compare that to the swp_entry_t
> obtained from linux page table pte. Leaking pte bits to swp_entry_t
> breaks that comparison and results in us looping in try_to_unuse.
> 
> The stack trace can be anywhere below try_to_unuse() in mm/swapfile.c,
> since swapoff is circling around and around that function, reading from
> each used swap block into a page, then trying to find where that page
> belongs, looking at every non-file pte of every mm that ever swapped.
> 
> Reported-by: Hugh Dickins <hughd@google.com>
> Suggested-by: Hugh Dickins <hughd@google.com>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Acked-by: Hugh Dickins <hughd@google.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/44734f23de2465c3c0d39e4a16

cheers