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    SubjectRe: [PATCH] driver core: Postpone DMA tear-down until after devres release for probe failure
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    On 11/04/2019 09:50, John Garry wrote:
    > On 04/04/2019 12:17, John Garry wrote:
    >> On 03/04/2019 10:20, John Garry wrote:
    >>> On 03/04/2019 09:14, Greg KH wrote:
    >>>> On Wed, Apr 03, 2019 at 09:02:36AM +0100, John Garry wrote:
    >>>>> On 28/03/2019 10:08, John Garry wrote:
    >>>>>> In commit 376991db4b64 ("driver core: Postpone DMA tear-down until
    >>>>>> after
    >>>>>> devres release"), we changed the ordering of tearing down the device
    >>>>>> DMA
    >>>>>> ops and releasing all the device's resources; this was because the
    >>>>>> DMA ops
    >>>>>> should be maintained until we release the device's managed DMA
    >>>>>> memories.
    >>>>>>
    >>>>>
    >>>>> Hi all,
    >>>>>
    >>>>> A friendly reminder on this patch... I didn't see any update.
    >>>>>
    >>>>> I thought that it had some importance.
    >>>>>
    >>>>> Thanks,
    >>>>> John
    >>>>>
    >>>>>> However, we have seen another crash on an arm64 system when a
    >>>>>> device driver probe fails:
    >>>>>>
    >>>>>>   hisi_sas_v3_hw 0000:74:02.0: Adding to iommu group 2
    >>>>>>   scsi host1: hisi_sas_v3_hw
    >>>>>>   BUG: Bad page state in process swapper/0  pfn:313f5
    >>>>>>   page:ffff7e0000c4fd40 count:1 mapcount:0
    >>>>>>   mapping:0000000000000000 index:0x0
    >>>>>>   flags: 0xfffe00000001000(reserved)
    >>>>>>   raw: 0fffe00000001000 ffff7e0000c4fd48 ffff7e0000c4fd48
    >>>>>> 0000000000000000
    >>>>>>   raw: 0000000000000000 0000000000000000 00000001ffffffff
    >>>>>> 0000000000000000
    >>>>>>   page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
    >>>>>>   bad because of flags: 0x1000(reserved)
    >>>>>>   Modules linked in:
    >>>>>>   CPU: 49 PID: 1 Comm: swapper/0 Not tainted
    >>>>>> 5.1.0-rc1-43081-g22d97fd-dirty #1433
    >>>>>>   Hardware name: Huawei D06/D06, BIOS Hisilicon D06 UEFI
    >>>>>> RC0 - V1.12.01 01/29/2019
    >>>>>>   Call trace:
    >>>>>>   dump_backtrace+0x0/0x118
    >>>>>>   show_stack+0x14/0x1c
    >>>>>>   dump_stack+0xa4/0xc8
    >>>>>>   bad_page+0xe4/0x13c
    >>>>>>   free_pages_check_bad+0x4c/0xc0
    >>>>>>   __free_pages_ok+0x30c/0x340
    >>>>>>   __free_pages+0x30/0x44
    >>>>>>   __dma_direct_free_pages+0x30/0x38
    >>>>>>   dma_direct_free+0x24/0x38
    >>>>>>   dma_free_attrs+0x9c/0xd8
    >>>>>>   dmam_release+0x20/0x28
    >>>>>>   release_nodes+0x17c/0x220
    >>>>>>   devres_release_all+0x34/0x54
    >>>>>>   really_probe+0xc4/0x2c8
    >>>>>>   driver_probe_device+0x58/0xfc
    >>>>>>   device_driver_attach+0x68/0x70
    >>>>>>   __driver_attach+0x94/0xdc
    >>>>>>   bus_for_each_dev+0x5c/0xb4
    >>>>>>   driver_attach+0x20/0x28
    >>>>>>   bus_add_driver+0x14c/0x200
    >>>>>>   driver_register+0x6c/0x124
    >>>>>>   __pci_register_driver+0x48/0x50
    >>>>>>   sas_v3_pci_driver_init+0x20/0x28
    >>>>>>   do_one_initcall+0x40/0x25c
    >>>>>>   kernel_init_freeable+0x2b8/0x3c0
    >>>>>>   kernel_init+0x10/0x100
    >>>>>>   ret_from_fork+0x10/0x18
    >>>>>>   Disabling lock debugging due to kernel taint
    >>>>>>   BUG: Bad page state in process swapper/0  pfn:313f6
    >>>>>>   page:ffff7e0000c4fd80 count:1 mapcount:0
    >>>>>> mapping:0000000000000000 index:0x0
    >>>>>> [   89.322983] flags: 0xfffe00000001000(reserved)
    >>>>>>   raw: 0fffe00000001000 ffff7e0000c4fd88 ffff7e0000c4fd88
    >>>>>> 0000000000000000
    >>>>>>   raw: 0000000000000000 0000000000000000 00000001ffffffff
    >>>>>> 0000000000000000
    >>>>>>
    >>>>>> The crash occurs for the same reason.
    >>>>>>
    >>>>>> In this case, on the really_probe() failure path, we are still
    >>>>>> clearing
    >>>>>> the DMA ops prior to releasing the device's managed memories.
    >>>>>>
    >>>>>> This patch fixes this issue by reordering the DMA ops teardown and
    >>>>>> the
    >>>>>> call to devres_release_all() on the failure path.
    >>>>>>
    >>>>>> Reported-by: Xiang Chen <chenxiang66@hisilicon.com>
    >>>>>> Tested-by: Xiang Chen <chenxiang66@hisilicon.com>
    >>>>>> Signed-off-by: John Garry <john.garry@huawei.com>
    >>>>
    >>>> So does this "fix" 376991db4b64?  If so, should this be added to the
    >>>> patch and also backported to the stable trees?
    >>>
    >>> Hi Greg,
    >>>
    >>> No, I don't think so. I'd say it supplements it. Here I'm trying to fix
    >>> up another path in which we tear down the DMA ops prior to releasing the
    >>> device's resources.
    >>>
    >>> I didn't add a fixes tag as 376991db4b64 didn't have one either. It will
    >>> need to be backported to stable, I figure the same as 376991db4b64.
    >>
    >
    > Hi Greg,
    >
    > I still think that we should consider merging this patch.

    Bah, sorry, I thought I'd replied to this thread already, but apparently
    not :(

    I don't have a particularly strong opinion, but at the moment I am
    leaning slightly towards this being a parallel fix for another part of
    09515ef5ddad, rather than a specific fix of the other fix. Either way,
    you can have a:

    Reviewed-by: Robin Murphy <robin.murphy@arm.com>

    Thanks,
    Robin.

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