linux-kernel - Re: [PATCH] soc: qcom: mdt_loader: Deal with zero e

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Message-ID: <490f9017-629d-4c19-8c2a-7fd106b4568c@linaro.org>
Date: Thu, 31 Jul 2025 16:58:09 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Val Packett <val@...kett.cool>
Subject: Re: [PATCH] soc: qcom: mdt_loader: Deal with zero e_shentsize

On 30/07/2025 22:51, Bjorn Andersson wrote:
> Firmware that doesn't provide section headers leave both e_shentsize and
> e_shnum 0, which obvious isn't compatible with the newly introduced
> stricter checks.
> 
> Make the section-related checks conditional on either of these values
> being non-zero.
> 
Missing:
Fixes: 9f35ab0e53cc ("soc: qcom: mdt_loader: Fix error return values in mdt_header_valid()")

Or it won't apply on stable kernels

> Fixes: 9f9967fed9d0 ("soc: qcom: mdt_loader: Ensure we don't read past the ELF header")
> Reported-by: Val Packett <val@...kett.cool>
> Closes: https://lore.kernel.org/all/ece307c3-7d65-440f-babd-88cf9705b908@packett.cool/
> Reported-by: Neil Armstrong <neil.armstrong@...aro.org>
> Closes: https://lore.kernel.org/all/aec9cd03-6fc2-4dc8-b937-8b7cf7bf4128@linaro.org/
> Signed-off-by: Bjorn Andersson <bjorn.andersson@....qualcomm.com>
> ---
>   drivers/soc/qcom/mdt_loader.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/soc/qcom/mdt_loader.c b/drivers/soc/qcom/mdt_loader.c
> index 0ca268bdf1f8c579b36a04fd94417be172fc1099..5710ac0c07a8c8a56110e3fc5e30b8610e106449 100644
> --- a/drivers/soc/qcom/mdt_loader.c
> +++ b/drivers/soc/qcom/mdt_loader.c
> @@ -39,12 +39,14 @@ static bool mdt_header_valid(const struct firmware *fw)
>   	if (phend > fw->size)
>   		return false;
>   
> -	if (ehdr->e_shentsize != sizeof(struct elf32_shdr))
> -		return false;
> +	if (ehdr->e_shentsize || ehdr->e_shnum) {
> +		if (ehdr->e_shentsize != sizeof(struct elf32_shdr))
> +			return false;
>   
> -	shend = size_add(size_mul(sizeof(struct elf32_shdr), ehdr->e_shnum), ehdr->e_shoff);
> -	if (shend > fw->size)
> -		return false;
> +		shend = size_add(size_mul(sizeof(struct elf32_shdr), ehdr->e_shnum), ehdr->e_shoff);
> +		if (shend > fw->size)
> +			return false;
> +	}
>   
>   	return true;
>   }
> 
> ---
> base-commit: 79fb37f39b77bbf9a56304e9af843cd93a7a1916
> change-id: 20250730-mdt-loader-shentsize-zero-8c99653b6343
> 
> Best regards,

Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8650-QRD

Thanks,
Neil