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    Subject[PATCH 4.19 145/149] driver core: Postpone DMA tear-down until after devres release
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Geert Uytterhoeven <geert+renesas@glider.be>

    commit 376991db4b6464e906d699ef07681e2ffa8ab08c upstream.

    When unbinding the (IOMMU-enabled) R-Car SATA device on Salvator-XS
    (R-Car H3 ES2.0), in preparation of rebinding against vfio-platform for
    device pass-through for virtualization:

        echo ee300000.sata > /sys/bus/platform/drivers/sata_rcar/unbind

    the kernel crashes with:

        Unable to handle kernel paging request at virtual address ffffffbf029ffffc
        Mem abort info:
          ESR = 0x96000006
          Exception class = DABT (current EL), IL = 32 bits
          SET = 0, FnV = 0
          EA = 0, S1PTW = 0
        Data abort info:
          ISV = 0, ISS = 0x00000006
          CM = 0, WnR = 0
        swapper pgtable: 4k pages, 39-bit VAs, pgdp = 000000007e8c586c
        [ffffffbf029ffffc] pgd=000000073bfc6003, pud=000000073bfc6003, pmd=0000000000000000
        Internal error: Oops: 96000006 [#1] SMP
        Modules linked in:
        CPU: 0 PID: 1098 Comm: bash Not tainted 5.0.0-rc5-salvator-x-00452-g37596f884f4318ef #287
        Hardware name: Renesas Salvator-X 2nd version board based on r8a7795 ES2.0+ (DT)
        pstate: 60400005 (nZCv daif +PAN -UAO)
        pc : __free_pages+0x8/0x58
        lr : __dma_direct_free_pages+0x50/0x5c
        sp : ffffff801268baa0
        x29: ffffff801268baa0 x28: 0000000000000000
        x27: ffffffc6f9c60bf0 x26: ffffffc6f9c60bf0
        x25: ffffffc6f9c60810 x24: 0000000000000000
        x23: 00000000fffff000 x22: ffffff8012145000
        x21: 0000000000000800 x20: ffffffbf029fffc8
        x19: 0000000000000000 x18: ffffffc6f86c42c8
        x17: 0000000000000000 x16: 0000000000000070
        x15: 0000000000000003 x14: 0000000000000000
        x13: ffffff801103d7f8 x12: 0000000000000028
        x11: ffffff8011117604 x10: 0000000000009ad8
        x9 : ffffff80110126d0 x8 : ffffffc6f7563000
        x7 : 6b6b6b6b6b6b6b6b x6 : 0000000000000018
        x5 : ffffff8011cf3cc8 x4 : 0000000000004000
        x3 : 0000000000080000 x2 : 0000000000000001
        x1 : 0000000000000000 x0 : ffffffbf029fffc8
        Process bash (pid: 1098, stack limit = 0x00000000c38e3e32)
        Call trace:
         __free_pages+0x8/0x58
         __dma_direct_free_pages+0x50/0x5c
         arch_dma_free+0x1c/0x98
         dma_direct_free+0x14/0x24
         dma_free_attrs+0x9c/0xdc
         dmam_release+0x18/0x20
         release_nodes+0x25c/0x28c
         devres_release_all+0x48/0x4c
         device_release_driver_internal+0x184/0x1f0
         device_release_driver+0x14/0x1c
         unbind_store+0x70/0xb8
         drv_attr_store+0x24/0x34
         sysfs_kf_write+0x4c/0x64
         kernfs_fop_write+0x154/0x1c4
         __vfs_write+0x34/0x164
         vfs_write+0xb4/0x16c
         ksys_write+0x5c/0xbc
         __arm64_sys_write+0x14/0x1c
         el0_svc_common+0x98/0x114
         el0_svc_handler+0x1c/0x24
         el0_svc+0x8/0xc
        Code: d51b4234 17fffffa a9bf7bfd 910003fd (b9403404)
        ---[ end trace 8c564cdd3a1a840f ]---

    While I've bisected this to commit e8e683ae9a736407 ("iommu/of: Fix
    probe-deferral"), and reverting that commit on post-v5.0-rc4 kernels
    does fix the problem, this turned out to be a red herring.

    On arm64, arch_teardown_dma_ops() resets dev->dma_ops to NULL.
    Hence if a driver has used a managed DMA allocation API, the allocated
    DMA memory will be freed using the direct DMA ops, while it may have
    been allocated using a custom DMA ops (iommu_dma_ops in this case).

    Fix this by reversing the order of the calls to devres_release_all() and
    arch_teardown_dma_ops().

    Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
    Acked-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Cc: stable <stable@vger.kernel.org>
    Reviewed-by: Robin Murphy <robin.murphy@arm.com>
    [rm: backport for 4.12-4.19 - kernels before 5.0 will not see
    the crash above, but may get silent memory corruption instead]
    Signed-off-by: Robin Murphy <robin.murphy@arm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/base/dd.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/base/dd.c
    +++ b/drivers/base/dd.c
    @@ -963,9 +963,9 @@ static void __device_release_driver(stru
    drv->remove(dev);

    device_links_driver_cleanup(dev);
    - dma_deconfigure(dev);

    devres_release_all(dev);
    + dma_deconfigure(dev);
    dev->driver = NULL;
    dev_set_drvdata(dev, NULL);
    if (dev->pm_domain && dev->pm_domain->dismiss)

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