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

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Date: Tue, 12 Mar 2024 12:35:46 +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 11:27 AM, Auditya Bhattaram wrote:
> 
> 
> 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]"
> 

Any further questions on this Bjorn.

>>> 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
>>>