linux-kernel - Re: [PATCH v3 1/5] soc: qcom: Introduce QMI encoder/decoder

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Date:   Thu, 16 Nov 2017 10:57:32 -0800
From:   Chris Lew <clew@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <andy.gross@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>
Cc:     Arun Kumar Neelakantam <aneela@...eaurora.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-soc@...r.kernel.org, linux-remoteproc@...r.kernel.org
Subject: Re: [PATCH v3 1/5] soc: qcom: Introduce QMI encoder/decoder



On 11/15/2017 9:42 PM, Bjorn Andersson wrote:
> On Wed 15 Nov 12:10 PST 2017, Bjorn Andersson wrote:
>> diff --git a/drivers/soc/qcom/qmi_encdec.c b/drivers/soc/qcom/qmi_encdec.c
> [..]
>> +void *qmi_encode_message(int type, unsigned int msg_id, size_t *len,
>> +			 unsigned int txn_id, struct qmi_elem_info *ei,
>> +			 const void *c_struct)
>> +{
>> +	struct qmi_header *hdr;
>> +	ssize_t msglen = 0;
>> +	void *msg;
>> +	int ret;
>> +
>> +	/* Check the possibility of a zero length QMI message */
>> +	if (!c_struct) {
>> +		ret = qmi_calc_min_msg_len(ei, 1);
>> +		if (ret) {
>> +			pr_err("%s: Calc. len %d != 0, but NULL c_struct\n",
>> +			       __func__, ret);
>> +			return ERR_PTR(-EINVAL);
>> +		}
>> +	}
>> +
>> +	msg = kzalloc(sizeof(*hdr) + *len, GFP_KERNEL);
>> +	if (!msg)
>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	msglen = qmi_encode(ei, msg + sizeof(*hdr), c_struct, *len, 1);
>> +	if (msglen < 0) {
>> +		kfree(msg);
>> +		return ERR_PTR(msglen);
>> +	}
> 
> Talked to Chris Lew about this earlier today;
> 
> The check above implies that it's valid to call this function with a
> valid ei of minimum message length of 0 and c_struct being NULL. But the
> call to qmi_encdec() will dereference c_struct in order to know that the
> optional elements described in ei are unset.
> 
> So the call to qmi_encode() needs to only be done conditionally on
> c_struct being non-NULL, logically interpreting c_struct being NULL as
> all optional fields are unset.
> 
> Will post an update with this fixed.
> 

I have tested this patch with QMI loopback servers, Qualcomm diag and 
slimbus ngd.

Tested-By: Chris Lew <clew@...eaurora.org>
>> +
>> +	hdr = msg;
>> +	hdr->type = type;
>> +	hdr->txn_id = txn_id;
>> +	hdr->msg_id = msg_id;
>> +	hdr->msg_len = msglen;
>> +
>> +	*len = sizeof(*hdr) + msglen;
>> +
>> +	return msg;
>> +}
>> +EXPORT_SYMBOL(qmi_encode_message);
> 
> Regards,
> Bjorn
> 

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