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

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Message-ID: <aNOehr6hxdb2OypO@stanley.mountain>
Date: Wed, 24 Sep 2025 10:32:22 +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 08:48:29AM +1000, 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.

Only the first iteration has been accessed.  The rest no.

regards,
dan carpenter