linux-kernel - Re: [RESEND 3/3] venus: handle use after free for iommu_map/iommu

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Message-ID: <c16db389-cdba-0735-a25e-8d5063d998cf@linaro.org>
Date:   Mon, 10 Aug 2020 12:53:22 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Mansur Alisha Shaik <mansur@...eaurora.org>,
        linux-media@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        vgarodia@...eaurora.org
Subject: Re: [RESEND 3/3] venus: handle use after free for
 iommu_map/iommu_unmap

Hi,

On 8/7/20 9:24 AM, Mansur Alisha Shaik wrote:
> In concurrency usecase and reboot scenario we are trying
> to map fw.iommu_domain which is already unmapped during

I guess you want to say "to unmap iommu domain which is already unmapped" ?

> shutdown. This is causing NULL pointer dereference crash.
> 
> This case is handled by adding necessary checks.
> 
> Call trace:
>  __iommu_map+0x4c/0x348
>  iommu_map+0x5c/0x70
>  venus_boot+0x184/0x230 [venus_core]
>  venus_sys_error_handler+0xa0/0x14c [venus_core]
>  process_one_work+0x210/0x3d0
>  worker_thread+0x248/0x3f4
>  kthread+0x11c/0x12c
>  ret_from_fork+0x10/0x18
> 
> Signed-off-by: Mansur Alisha Shaik <mansur@...eaurora.org>
> ---
>  drivers/media/platform/qcom/venus/firmware.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/venus/firmware.c b/drivers/media/platform/qcom/venus/firmware.c
> index 8801a6a..c427e88 100644
> --- a/drivers/media/platform/qcom/venus/firmware.c
> +++ b/drivers/media/platform/qcom/venus/firmware.c
> @@ -171,9 +171,14 @@ static int venus_shutdown_no_tz(struct venus_core *core)
>  
>  	iommu = core->fw.iommu_domain;
>  
> -	unmapped = iommu_unmap(iommu, VENUS_FW_START_ADDR, mapped);
> -	if (unmapped != mapped)
> -		dev_err(dev, "failed to unmap firmware\n");
> +	if (core->fw.mapped_mem_size && iommu) {
> +		unmapped = iommu_unmap(iommu, VENUS_FW_START_ADDR, mapped);
> +
> +		if (unmapped != mapped)
> +			dev_err(dev, "failed to unmap firmware\n");
> +		else
> +			core->fw.mapped_mem_size = 0;
> +	}
>  
>  	return 0;
>  }
> @@ -288,7 +293,11 @@ void venus_firmware_deinit(struct venus_core *core)
>  	iommu = core->fw.iommu_domain;
>  
>  	iommu_detach_device(iommu, core->fw.dev);
> -	iommu_domain_free(iommu);
> +
> +	if (core->fw.iommu_domain) {
> +		iommu_domain_free(iommu);
> +		core->fw.iommu_domain = NULL;
> +	}
>  
>  	platform_device_unregister(to_platform_device(core->fw.dev));
>  }
> 

-- 
regards,
Stan