linux-kernel - Re: [PATCH v1] soc: qcom: mdt_loader: Add Upperbounds check for program header access

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Date: Fri, 2 Feb 2024 13:34:54 +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>
Subject: Re: [PATCH v1] soc: qcom: mdt_loader: Add Upperbounds check for
 program header access


This should be v2., first time patches is always counted as v1

On 2/2/2024 12:09 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.
> 
> Signed-off-by: Auditya Bhattaram <quic_audityab@...cinc.com> > ---
> Added error prints for Invalid access.
> Link for previous discussion https://lore.kernel.org/linux-arm-msm/5d7a3b97-d840-4863-91a0-32c1d8e7532f@linaro.org/T/#t

Would be better if you take reference from other patches,

Like above can be done as,

Changes in v2:
   -  ...
   -  ,,,
> ---
>   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)) {
> +		dev_err(dev, "Invalid phdrs access: %s\n", fw_name);
> +		return ERR_PTR(-EINVAL);
> +	}
> +

Should this not be marked for stable kernel ? as without this it could 
be accessing beyond fw_size for uncertain scenario.

-Mukesh

>   	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
> 
>