linux-kernel - Re: [PATCH v4] soc: qcom: mdt_loader: Add Upperbounds check for program header access

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Date: Wed, 14 Feb 2024 11:27:01 +0530
From: Auditya Bhattaram <quic_audityab@...cinc.com>
To: Bjorn Andersson <andersson@...nel.org>
CC: <konrad.dybcio@...aro.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH v4] soc: qcom: mdt_loader: Add Upperbounds check for
 program header access



On 2/14/2024 11:12 AM, Bjorn Andersson wrote:
> On Tue, Feb 13, 2024 at 01:30:10PM +0530, 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.
>>
> 
> How is this compatible with what is being observed on SM8450 and
> implemented in commit 8bd42e2341a7 ("soc: qcom: mdt_loader: Allow hash
> segment to be split out"?
> 
> Regards,
> Bjorn
> 

Calculating hash_index is introduced with this commit 8bd42e2341a7 
("soc: qcom: mdt_loader: Allow hash segment to be split out"

     for (i = 1; i < ehdr->e_phnum; i++) {
  	if ((phdrs[i].p_flags & QCOM_MDT_TYPE_MASK) ...

I'm trying to add an upper bound for this access "phdrs[i]"

>> 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>
>> Acked-by: Mukesh Ojha <quic_mojha@...cinc.com>
>> ---
>> Changes in v4:
>>   - Added additional prints incase of Invalid access.
>> Link to v3 https://lore.kernel.org/stable/1c91c653-cebe-4407-bdd6-cfc73b64c0fb@quicinc.com
>> 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 | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/soc/qcom/mdt_loader.c b/drivers/soc/qcom/mdt_loader.c
>> index 6f177e46fa0f..1a79a7bba468 100644
>> --- a/drivers/soc/qcom/mdt_loader.c
>> +++ b/drivers/soc/qcom/mdt_loader.c
>> @@ -145,6 +143,13 @@ 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 for fw: %s, e_phnum: %u, fw->size: %zu\n",
>> +			fw_name, ehdr->e_phnum, fw->size);
>> +		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
>>