linux-kernel - Re: [PATCH v3] soc: qcom: mdt_loader: Add Upperbounds check for program header access

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Date: Thu, 8 Feb 2024 19:59:20 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: Auditya Bhattaram <quic_audityab@...cinc.com>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>
CC: <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v3] soc: qcom: mdt_loader: Add Upperbounds check for
 program header access



On 2/8/2024 6:05 PM, Auditya Bhattaram wrote:
> hash_index is evaluated by looping phdrs till QCOM_MDT_TYPE_HASH
> is found. Add an upperbound check to phdrs to access within elf size.
> 
> Fixes: 64fb5eb87d58 ("soc: qcom: mdt_loader: Allow hash to reside in any segment")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Auditya Bhattaram <quic_audityab@...cinc.com>
> ---
> Changes in v3:
>   - Corrected wrong patch versioning in the Subject.
>   - Added error prints for Invalid access.
> Link to v2 https://lore.kernel.org/linux-arm-msm/9773d189-c896-d5c5-804c-e086c24987b4@quicinc.com/T/#t
> Link to v1 https://lore.kernel.org/linux-arm-msm/5d7a3b97-d840-4863-91a0-32c1d8e7532f@linaro.org/T/#t
> ---
>   drivers/soc/qcom/mdt_loader.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/soc/qcom/mdt_loader.c b/drivers/soc/qcom/mdt_loader.c
> index 6f177e46fa0f..61e2377cc5c3 100644
> --- a/drivers/soc/qcom/mdt_loader.c
> +++ b/drivers/soc/qcom/mdt_loader.c
> @@ -145,6 +145,11 @@ void *qcom_mdt_read_metadata(const struct firmware *fw, size_t *data_len,
>   	if (phdrs[0].p_type == PT_LOAD)
>   		return ERR_PTR(-EINVAL);
> 
> +	if (((size_t)(phdrs + ehdr->e_phnum)) > ((size_t)ehdr + fw->size)) {

This change is valid only if somehow, ehdr->e_phnum gets corrupted or 
changed via some engineering means and results in out-of-bounds access.

Acked-by: Mukesh Ojha <quic_mojha@...cinc.com>

> +		dev_err(dev, "Invalid phdrs access: %s\n", fw_name);

Should it print ehdr->e_phnum as well to be more valid?

-Mukesh

> +		return ERR_PTR(-EINVAL);
> +	}
> +
>   	for (i = 1; i < ehdr->e_phnum; i++) {
>   		if ((phdrs[i].p_flags & QCOM_MDT_TYPE_MASK) == QCOM_MDT_TYPE_HASH) {
>   			hash_segment = i;
> --
> 2.17.1
> 
>