linux-kernel - Re: [PATCH] mm/device-public-memory: Fix edge case in _vm_normal

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Message-ID: <CAKTCnzk6k3q8Pkh=REVFuiXuf=faORziwUBSkq_eOchM7J1BHA@mail.gmail.com>
Date:   Sat, 23 Sep 2017 16:01:10 +1000
From:   Balbir Singh <bsingharora@...il.com>
To:     Reza Arbab <arbab@...ux.vnet.ibm.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jérôme Glisse <jglisse@...hat.com>
Subject: Re: [PATCH] mm/device-public-memory: Fix edge case in _vm_normal_page()

On Sat, Sep 23, 2017 at 12:56 AM, Reza Arbab <arbab@...ux.vnet.ibm.com> wrote:
> With device public pages at the end of my memory space, I'm getting
> output from _vm_normal_page():
>
> BUG: Bad page map in process migrate_pages  pte:c0800001ffff0d06 pmd:f95d3000
> addr:00007fff89330000 vm_flags:00100073 anon_vma:c0000000fa899320 mapping:          (null) index:7fff8933
> file:          (null) fault:          (null) mmap:          (null) readpage:          (null)
> CPU: 0 PID: 13963 Comm: migrate_pages Tainted: P    B      OE 4.14.0-rc1-wip #155
> Call Trace:
> [c0000000f965f910] [c00000000094d55c] dump_stack+0xb0/0xf4 (unreliable)
> [c0000000f965f950] [c0000000002b269c] print_bad_pte+0x28c/0x340
> [c0000000f965fa00] [c0000000002b59c0] _vm_normal_page+0xc0/0x140
> [c0000000f965fa20] [c0000000002b6e64] zap_pte_range+0x664/0xc10
> [c0000000f965fb00] [c0000000002b7858] unmap_page_range+0x318/0x670
> [c0000000f965fbd0] [c0000000002b8074] unmap_vmas+0x74/0xe0
> [c0000000f965fc20] [c0000000002c4a18] exit_mmap+0xe8/0x1f0
> [c0000000f965fce0] [c0000000000ecbdc] mmput+0xac/0x1f0
> [c0000000f965fd10] [c0000000000f62e8] do_exit+0x348/0xcd0
> [c0000000f965fdd0] [c0000000000f6d2c] do_group_exit+0x5c/0xf0
> [c0000000f965fe10] [c0000000000f6ddc] SyS_exit_group+0x1c/0x20
> [c0000000f965fe30] [c00000000000b184] system_call+0x58/0x6c
>
> The pfn causing this is the very last one. Correct the bounds check
> accordingly.
>
> Fixes: df6ad69838fc ("mm/device-public-memory: device memory cache coherent with CPU")
> Cc: Jérôme Glisse <jglisse@...hat.com>
> Signed-off-by: Reza Arbab <arbab@...ux.vnet.ibm.com>
> ---

Reviewed-by: Balbir Singh <bsingharora@...il.com>