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SubjectRe: [PATCH] drm/exynos: Fix memory leak and release IOMMU mapping structures
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Hi Lukasz,

On 04.03.2020 23:00, Lukasz Luba wrote:
> There is a memory leak which left some objects not freed. The reference
> counter of mapping: 'mapping->kref' was 2 when calling
> arm_iommu_detach_device(), so the release_iommu_mapping() won't be called.
> Since the old mapping structure is not going to be used any more (because
> it is detached and new one attached), call arm_iommu_release_mapping()
> to trigger cleanup.

This will break IOMMU support in Exynos DRM if deferred probe happens.
Here is a proper fix:

https://patchwork.kernel.org/patch/11415715/

The mapping initially created by DMA-mapping framework should be
attached back when Exynos DRM releases the subdev device.

> Found using kmemleak detector, the output:
>
> unreferenced object 0xc2137640 (size 64):
> comm "swapper/0", pid 1, jiffies 4294937900 (age 3127.400s)
> hex dump (first 32 bytes):
> 50 a3 14 c2 80 a2 14 c2 01 00 00 00 20 00 00 00 P........... ...
> 00 10 00 00 00 80 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<3acd268d>] arch_setup_dma_ops+0x4c/0x104
> [<9f7d2cce>] of_dma_configure+0x19c/0x3a4
> [<ba07704b>] really_probe+0xb0/0x47c
> [<4f510e4f>] driver_probe_device+0x78/0x1c4
> [<7481a0cf>] device_driver_attach+0x58/0x60
> [<0ff8f5c1>] __driver_attach+0xb8/0x158
> [<86006144>] bus_for_each_dev+0x74/0xb4
> [<10159dca>] bus_add_driver+0x1c0/0x200
> [<8a265265>] driver_register+0x74/0x108
> [<e0f3451a>] exynos_drm_init+0xb0/0x134
> [<db3fc7ba>] do_one_initcall+0x90/0x458
> [<6da35917>] kernel_init_freeable+0x188/0x200
> [<db3f74d4>] kernel_init+0x8/0x110
> [<1f3cddf9>] ret_from_fork+0x14/0x20
> [<8cd12507>] 0x0
> unreferenced object 0xc214a280 (size 128):
> comm "swapper/0", pid 1, jiffies 4294937900 (age 3127.400s)
> hex dump (first 32 bytes):
> 00 a0 ec ed 00 00 00 00 00 00 00 00 00 00 00 00 ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<3acd268d>] arch_setup_dma_ops+0x4c/0x104
> [<9f7d2cce>] of_dma_configure+0x19c/0x3a4
> [<ba07704b>] really_probe+0xb0/0x47c
> [<4f510e4f>] driver_probe_device+0x78/0x1c4
> [<7481a0cf>] device_driver_attach+0x58/0x60
> [<0ff8f5c1>] __driver_attach+0xb8/0x158
> [<86006144>] bus_for_each_dev+0x74/0xb4
> [<10159dca>] bus_add_driver+0x1c0/0x200
> [<8a265265>] driver_register+0x74/0x108
> [<e0f3451a>] exynos_drm_init+0xb0/0x134
> [<db3fc7ba>] do_one_initcall+0x90/0x458
> [<6da35917>] kernel_init_freeable+0x188/0x200
> [<db3f74d4>] kernel_init+0x8/0x110
> [<1f3cddf9>] ret_from_fork+0x14/0x20
> [<8cd12507>] 0x0
> unreferenced object 0xedeca000 (size 4096):
> comm "swapper/0", pid 1, jiffies 4294937900 (age 3127.400s)
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<3acd268d>] arch_setup_dma_ops+0x4c/0x104
> [<9f7d2cce>] of_dma_configure+0x19c/0x3a4
> [<ba07704b>] really_probe+0xb0/0x47c
> [<4f510e4f>] driver_probe_device+0x78/0x1c4
> [<7481a0cf>] device_driver_attach+0x58/0x60
> [<0ff8f5c1>] __driver_attach+0xb8/0x158
> [<86006144>] bus_for_each_dev+0x74/0xb4
> [<10159dca>] bus_add_driver+0x1c0/0x200
> [<8a265265>] driver_register+0x74/0x108
> [<e0f3451a>] exynos_drm_init+0xb0/0x134
> [<db3fc7ba>] do_one_initcall+0x90/0x458
> [<6da35917>] kernel_init_freeable+0x188/0x200
> [<db3f74d4>] kernel_init+0x8/0x110
> [<1f3cddf9>] ret_from_fork+0x14/0x20
> [<8cd12507>] 0x0
> unreferenced object 0xc214a300 (size 128):
> comm "swapper/0", pid 1, jiffies 4294937900 (age 3127.400s)
> hex dump (first 32 bytes):
> 00 a3 14 c2 00 a3 14 c2 00 40 18 c2 00 80 18 c2 .........@......
> 02 00 02 00 ad 4e ad de ff ff ff ff ff ff ff ff .....N..........
> backtrace:
> [<08cbd8bc>] iommu_domain_alloc+0x24/0x50
> [<b835abee>] arm_iommu_create_mapping+0xe4/0x134
> [<3acd268d>] arch_setup_dma_ops+0x4c/0x104
> [<9f7d2cce>] of_dma_configure+0x19c/0x3a4
> [<ba07704b>] really_probe+0xb0/0x47c
> [<4f510e4f>] driver_probe_device+0x78/0x1c4
> [<7481a0cf>] device_driver_attach+0x58/0x60
> [<0ff8f5c1>] __driver_attach+0xb8/0x158
> [<86006144>] bus_for_each_dev+0x74/0xb4
> [<10159dca>] bus_add_driver+0x1c0/0x200
> [<8a265265>] driver_register+0x74/0x108
> [<e0f3451a>] exynos_drm_init+0xb0/0x134
> [<db3fc7ba>] do_one_initcall+0x90/0x458
> [<6da35917>] kernel_init_freeable+0x188/0x200
> [<db3f74d4>] kernel_init+0x8/0x110
> [<1f3cddf9>] ret_from_fork+0x14/0x20
>
> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
> ---
>
> Hi all,
>
> I have discovered this issue on OdroidXU4 while running some stress tests
> for upcoming Energy Model. To reproduce it, kernel must be compiled with
> DEBUG_KMEMLEAK. When the boot has finished, type:
> # echo scan > /sys/kernel/debug/kmemleak
> # cat /sys/kernel/debug/kmemleak
> You should expect similar output to the one from the commit message.
>
> I don't know if it should go via stable tree as well. I can resend with CC
> stable, if there is a need.
>
> Regards,
> Lukasz Luba
>
> drivers/gpu/drm/exynos/exynos_drm_dma.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dma.c b/drivers/gpu/drm/exynos/exynos_drm_dma.c
> index 9ebc02768847..45f209ec107f 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_dma.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_dma.c
> @@ -74,8 +74,13 @@ static int drm_iommu_attach_device(struct drm_device *drm_dev,
> return ret;
>
> if (IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)) {
> - if (to_dma_iommu_mapping(subdrv_dev))
> + struct dma_iommu_mapping *mapping =
> + to_dma_iommu_mapping(subdrv_dev);
> +
> + if (mapping) {
> arm_iommu_detach_device(subdrv_dev);
> + arm_iommu_release_mapping(mapping);
> + }
>
> ret = arm_iommu_attach_device(subdrv_dev, priv->mapping);
> } else if (IS_ENABLED(CONFIG_IOMMU_DMA)) {

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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