Re: [PATCH] iommu/mediatek: Fix NULL pointer deference in mtk_iommu_device_group

["Yong Wu (吴勇)" <Yong.Wu@mediatek.com>]

On Thu, 2025-03-27 at 11:46 +0100, Louis-Alexis Eyraud wrote:
> External email : Please do not click links or open attachments until
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> 
> 
> Currently, mtk_iommu calls during probe iommu_device_register before
> the hw_list from driver data is initialized. Since iommu probing
> issue
> fix, it leads to NULL pointer dereference in mtk_iommu_device_group
> when
> hw_list is accessed with list_first_entry (not null safe).
> 
> So, change the call order to ensure iommu_device_register is called
> after the driver data are initialized.
> 
> Fixes: 9e3a2a643653 ("iommu/mediatek: Adapt sharing and non-sharing
> pgtable case")
> Fixes: bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper
> probe path")
> Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
> ---
> This patch fixes a NULL pointer dereference that occurs during the
> mtk_iommu driver probe and observed at least on several Mediatek
> Genio boards:
> ```
> Unable to handle kernel NULL pointer dereference at virtual address
> 0000000000000000
> Mem abort info:
>   ESR = 0x0000000096000004
>   EC = 0x25: DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x04: level 0 translation fault
> Data abort info:
>   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
>   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
>   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> user pgtable: 4k pages, 48-bit VAs, pgdp=0000000101380000
> [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
> Internal error: Oops: 0000000096000004 [#1]  SMP
> Modules linked in: btusb btrtl mt6315_regulator btintel
> mtk_vcodec_dec
>   btmtk v4l2_vp9 btbcm mtk_vcodec_enc v4l2_h264 mtk_vcodec_dbgfs
>   bluetooth mtk_jpeg ecdh_generic mtk_vcodec_common mtk_jpeg_enc_hw
>   mtk_jpeg_dec_hw ecc v4l2_mem2mem rfkill videobuf2_dma_contig
>   videobuf2_memops videobuf2_v4l2 videodev videobuf2_common mc
>   mt6360_charger mcp251xfd it5205 goodix_ts can_dev panfrost
>   drm_shmem_helper gpu_sched lvts_thermal mtk_svs mtk_adsp_mailbox
>   snd_soc_dmic mtk_scp mtk_rpmsg mtk_scp_ipi mtk_cmdq_mailbox
>   mediatek_cpufreq_hw spmi_mtk_pmif fuse dm_mod ip_tables x_tables
>   ipv6 mediatek_drm tcpci_mt6360 drm_display_helper drm_client_lib
>   tcpci drm_dma_helper drm_kms_helper tcpm drm mtk_mutex mtk_mmsys
>   typec rtc_mt6397 mtk_cmdq_helper phy_mtk_pcie pcie_mediatek_gen3
>   dwmac_mediatek stmmac_platform stmmac pwm_mtk_disp pcs_xpcs pwm_bl
>   backlight
> CPU: 5 UID: 0 PID: 12 Comm: kworker/u32:0 Not tainted 6.14.0-next-
> 20250326 #4 PREEMPT
> Hardware name: MediaTek Genio 1200 EVK-P1V2-EMMC (DT)
> Workqueue: events_unbound deferred_probe_work_func
> pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : mtk_iommu_device_group+0x2c/0xe0
> lr : __iommu_probe_device+0x130/0x490
> sp : ffff8000827b3970
> x29: ffff8000827b3970 x28: ffff0000c0028000 x27: ffff80008164f2b8
> x26: ffff0000cbc47130 x25: ffff80008096a9f0 x24: ffff80008164f5a8
> x23: ffff800082684b60 x22: ffff8000827b3a80 x21: ffff0000cbc47130
> x20: ffffffffffffffed x19: ffff0000c117c010 x18: 0000000000000000
> x17: 6f702d616d642d64 x16: 6574636972747365 x15: 0000000000000002
> x14: 0000000000000000 x13: 0000000000128d55 x12: 6f632d616d642e30
> x11: 0000000000000100 x10: 0000000000000001 x9 : 0000000000000220
> x8 : 0101010101010101 x7 : ffff0000c117c010 x6 : 306c766f2c727461
> x5 : 0000000000000000 x4 : ffff0000c10a2de8 x3 : ffff0000c10a2e70
> x2 : ffff0000c01a4600 x1 : 0000000000000000 x0 : ffff0000c65470c0
> Call trace:
>  mtk_iommu_device_group+0x2c/0xe0 (P)
>  __iommu_probe_device+0x130/0x490
>  probe_iommu_group+0x3c/0x70
>  bus_for_each_dev+0x7c/0xe0
>  iommu_device_register+0xd8/0x22c
>  mtk_iommu_probe+0x270/0x53c
>  platform_probe+0x68/0xd8
>  really_probe+0xbc/0x2c0
>  __driver_probe_device+0x78/0x120
>  driver_probe_device+0x3c/0x154
>  __device_attach_driver+0xb8/0x140
>  bus_for_each_drv+0x88/0xe8
>  __device_attach+0xa0/0x190
>  device_initial_probe+0x14/0x20
>  bus_probe_device+0xb4/0xc0
>  deferred_probe_work_func+0x90/0xc8
>  process_one_work+0x148/0x284
>  worker_thread+0x2cc/0x3cc
>  kthread+0x12c/0x204
>  ret_from_fork+0x10/0x20
> Code: b4000500 f9401c01 92800254 f9409821 (f9400035)
> ---[ end trace 0000000000000000 ]---
> ```
> 
> I've tested this patch on Mediatek Genio 510-EVK and 1200-EVK boards
> with a kernel based on linux-next (tag: next-20250327).
> ---
>  drivers/iommu/mtk_iommu.c | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index
> 034b0e670384a24df10130cbbff95ce8e0bc092d..14adb96a37bb0d84b631188e48d
> d8b936821a717 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -1372,15 +1372,6 @@ static int mtk_iommu_probe(struct
> platform_device *pdev)
>         platform_set_drvdata(pdev, data);
>         mutex_init(&data->mutex);
> 
> -       ret = iommu_device_sysfs_add(&data->iommu, dev, NULL,
> -                                    "mtk-iommu.%pa", &ioaddr);
> -       if (ret)
> -               goto out_link_remove;
> -
> -       ret = iommu_device_register(&data->iommu, &mtk_iommu_ops,
> dev);
> -       if (ret)
> -               goto out_sysfs_remove;
> -
>         if (MTK_IOMMU_HAS_FLAG(data->plat_data, SHARE_PGTABLE)) {
>                 list_add_tail(&data->list, data->plat_data->hw_list);
>                 data->hw_list = data->plat_data->hw_list;
> @@ -1390,18 +1381,28 @@ static int mtk_iommu_probe(struct
> platform_device *pdev)
>                 data->hw_list = &data->hw_list_head;
>         }
> 
> +       ret = iommu_device_sysfs_add(&data->iommu, dev, NULL,
> +                                    "mtk-iommu.%pa", &ioaddr);
> +       if (ret)
> +               goto out_list_del;
> +
> +       ret = iommu_device_register(&data->iommu, &mtk_iommu_ops,
> dev);
> +       if (ret)
> +               goto out_link_remove;


Typo here. Use out_sysfs_remove instead and remove out_link_remove
label. Then,

Reviewed-by: Yong Wu <yong.wu@mediatek.com>

Thanks very much for this patch.

> +
>         if (MTK_IOMMU_IS_TYPE(data->plat_data, MTK_IOMMU_TYPE_MM)) {
>                 ret = component_master_add_with_match(dev,
> &mtk_iommu_com_ops, match);
>                 if (ret)
> -                       goto out_list_del;
> +                       goto out_device_unregister;
>         }
>         return ret;
> 
> -out_list_del:
> -       list_del(&data->list);
> +out_device_unregister:
>         iommu_device_unregister(&data->iommu);
>  out_sysfs_remove:
>         iommu_device_sysfs_remove(&data->iommu);
> +out_list_del:
> +       list_del(&data->list);
>  out_link_remove:
>         if (MTK_IOMMU_IS_TYPE(data->plat_data, MTK_IOMMU_TYPE_MM))
>                 device_link_remove(data->smicomm_dev, dev);
> 
> ---
> base-commit: bc960e3e32c8b940c10b14557271355f66ae4db1
> change-id: 20250327-fix-mtk-iommu-error-af6ec347d057
> 
> Best regards,
> --
> Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
>