linux-kernel - Re: [PATCH v3 6/9] bus: mhi: core: WARN

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Message-ID: <15f88b7a-a3cb-ac19-bffe-247f2e99d894@codeaurora.org>
Date:   Thu, 30 Apr 2020 09:02:19 -0600
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>, mani@...nel.org
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        hemantk@...eaurora.org
Subject: Re: [PATCH v3 6/9] bus: mhi: core: WARN_ON for malformed vector table

On 4/29/2020 2:52 PM, Bhaumik Bhatt wrote:
> Add a bounds check in the firmware copy routine to exit if a malformed
> vector table is found while attempting to load the firmware in to the
> BHIe vector table.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
> ---
>   drivers/bus/mhi/core/boot.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/bus/mhi/core/boot.c b/drivers/bus/mhi/core/boot.c
> index 17c636b..bc70edc 100644
> --- a/drivers/bus/mhi/core/boot.c
> +++ b/drivers/bus/mhi/core/boot.c
> @@ -362,8 +362,14 @@ static void mhi_firmware_copy(struct mhi_controller *mhi_cntrl,
>   	int i = 0;
>   	struct mhi_buf *mhi_buf = img_info->mhi_buf;
>   	struct bhi_vec_entry *bhi_vec = img_info->bhi_vec;
> +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>   
>   	while (remainder) {
> +		if (WARN_ON(i >= img_info->entries)) {
> +			dev_err(dev, "Malformed vector table\n");

I feel like this message needs more detail.  At a minimum, I think it 
should indicate what vector table (BHIe).  I think if you can identify 
what file, etc the the glitch is in, that would be better.  Maybe some 
detail about i and img_info->entries.

If I see this error message, I should have enough information to 
immediately debug the issue.  If it tells enough to go directly into the 
firmware file and have a look at entry X to see what might be corrupt 
about it, that makes my debugging very efficient.  If I have to go back 
to the code to figure out what "Malformed vector table" means, and then 
maybe apply a patch to get more data about the error - the error message 
is not as useful as it should be.

> +			return;
> +		}
> +
>   		to_cpy = min(remainder, mhi_buf->len);
>   		memcpy(mhi_buf->buf, buf, to_cpy);
>   		bhi_vec->dma_addr = mhi_buf->dma_addr;
> 

-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.