linux-kernel - Re: [PATCH] driver core: Free DMA range map when device is released

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Date:   Wed, 16 Feb 2022 09:45:09 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Mårten Lindahl <marten.lindahl@...s.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>, kernel <kernel@...s.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] driver core: Free DMA range map when device is released

On Wed, Feb 16, 2022 at 3:42 AM Mårten Lindahl <marten.lindahl@...s.com> wrote:
>
> When unbinding/binding a driver with DMA mapped memory, the DMA map is
> not freed before the driver is reloaded. This leads to a memory leak
> when the DMA map is overwritten when reprobing the driver.
>
> This can be reproduced with a platform driver having a dma-range:
>
> dummy {
>         ...
>         #address-cells = <0x2>;
>         #size-cells = <0x2>;
>         ranges;
>         dma-ranges = <...>;
>         ...
> };
>
> and then unbinding/binding it:
>
> ~# echo soc:dummy >/sys/bus/platform/drivers/<driver>/unbind
>
> DMA map object 0xffffff800b0ae540 still being held by &pdev->dev
>
> ~# echo soc:dummy >/sys/bus/platform/drivers/<driver>/bind
> ~# echo scan > /sys/kernel/debug/kmemleak
> ~# cat /sys/kernel/debug/kmemleak
> unreferenced object 0xffffff800b0ae540 (size 64):
>   comm "sh", pid 833, jiffies 4295174550 (age 2535.352s)
>   hex dump (first 32 bytes):
>     00 00 00 80 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 80 00 00 00 00 00 00 00 80 00 00 00 00  ................
>   backtrace:
>     [<ffffffefd1694708>] create_object.isra.0+0x108/0x344
>     [<ffffffefd1d1a850>] kmemleak_alloc+0x8c/0xd0
>     [<ffffffefd167e2d0>] __kmalloc+0x440/0x6f0
>     [<ffffffefd1a960a4>] of_dma_get_range+0x124/0x220
>     [<ffffffefd1a8ce90>] of_dma_configure_id+0x40/0x2d0
>     [<ffffffefd198b68c>] platform_dma_configure+0x5c/0xa4
>     [<ffffffefd198846c>] really_probe+0x8c/0x514
>     [<ffffffefd1988990>] __driver_probe_device+0x9c/0x19c
>     [<ffffffefd1988cd8>] device_driver_attach+0x54/0xbc
>     [<ffffffefd1986634>] bind_store+0xc4/0x120
>     [<ffffffefd19856e0>] drv_attr_store+0x30/0x44
>     [<ffffffefd173c9b0>] sysfs_kf_write+0x50/0x60
>     [<ffffffefd173c1c4>] kernfs_fop_write_iter+0x124/0x1b4
>     [<ffffffefd16a013c>] new_sync_write+0xdc/0x160
>     [<ffffffefd16a256c>] vfs_write+0x23c/0x2a0
>     [<ffffffefd16a2758>] ksys_write+0x64/0xec
>
> To prevent this we should free the dma_range_map when the device is
> released.
>
> Signed-off-by: Mårten Lindahl <marten.lindahl@...s.com>

Suggested-by: Rob Herring <robh@...nel.org>
Fixes: e0d072782c73 ("dma-mapping: introduce DMA range map,
supplanting dma_pfn_offset")
Reviewed-by: Rob Herring <robh@...nel.org>

I've got a follow-up patch to refactor the 3 occurrences of this same
deinit code.

Rob