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

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Message-ID: <aNOfXlG21HIBR18E@stanley.mountain>
Date: Wed, 24 Sep 2025 10:35:58 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>
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 Wed, Sep 24, 2025 at 08:58:45AM +1000, Amirreza Zarrabi wrote:
> 
> 
> 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).
> 

Yes.  This is true.

regards,
dan carpenter