linux-kernel - Re: [PATCH next] tee: qcom: prevent potential off by one read

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Message-ID: <bb776102-310b-4a84-943a-86d4138592d8@oss.qualcomm.com>
Date: Wed, 24 Sep 2025 08:58:45 +1000
From: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Jens Wiklander <jens.wiklander@...aro.org>,
        Sumit Garg <sumit.garg@...nel.org>, linux-arm-msm@...r.kernel.org,
        op-tee@...ts.trustedfirmware.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH next] tee: qcom: prevent potential off by one read



On 9/24/2025 8:48 AM, Amirreza Zarrabi wrote:
> On 9/18/2025 7:50 PM, Dan Carpenter wrote:
>> Re-order these checks to check if "i" is a valid array index before using
>> it.  This prevents a potential off by one read access.
>>
>> Fixes: d6e290837e50 ("tee: add Qualcomm TEE driver")
>> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
>> ---
>>  drivers/tee/qcomtee/call.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/tee/qcomtee/call.c b/drivers/tee/qcomtee/call.c
>> index cc17a48d0ab7..ac134452cc9c 100644
>> --- a/drivers/tee/qcomtee/call.c
>> +++ b/drivers/tee/qcomtee/call.c
>> @@ -308,7 +308,7 @@ static int qcomtee_params_from_args(struct tee_param *params,
>>  	}
>>  
>>  	/* Release any IO and OO objects not processed. */
>> -	for (; u[i].type && i < num_params; i++) {
>> +	for (; i < num_params && u[i].type; i++) {
>>  		if (u[i].type == QCOMTEE_ARG_TYPE_OO ||
>>  		    u[i].type == QCOMTEE_ARG_TYPE_IO)
>>  			qcomtee_object_put(u[i].o);
> 
> This is not required, considering the sequence of clean up, this
> would never happen. `i` at least have been accessed once in the
> switch above.
> 
> Regards,
> Amir
> 
>

Also, size of u is always num_params + 1 for the ending 0.
(basically means `i < num_params` can be removed).

Anyway, it does not hurt :).

Regards,
Amir