linux-kernel - Re: [PATCH v2 4/9] coresight: Fix csdev connections initialisation

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Message-ID: <CANLsYkwGckonnLjHbOJQPZ849NQyjf+Zy=N6kjtwwo-kQbbj4Q@mail.gmail.com>
Date:	Sun, 12 Jun 2016 14:39:27 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Suzuki K Poulose <suzuki.poulose@....com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/9] coresight: Fix csdev connections initialisation

On 6 June 2016 at 03:11, Suzuki K Poulose <suzuki.poulose@....com> wrote:
> This is a cleanup patch.
>
> coresight_device->conns holds an array to point to the devices
> connected to the OUT ports of a component. Sinks, e.g ETR, do not
> have an OUT port (nr_outport = 0), as it streams the trace to
> memory via AXI.
>
> At coresight_register() we do :
>
>         conns = kcalloc(csdev->nr_outport, sizeof(*conns), GFP_KERNEL);
>         if (!conns) {
>                 ret = -ENOMEM;
>                 goto err_kzalloc_conns;
>         }
>
> For ETR, since the total size requested for kcalloc is zero, the return
> value is, ZERO_SIZE_PTR ( != NULL). Hence, csdev->conns = ZERO_SIZE_PTR
> which cannot be verified later to contain a valid pointer. The code which
> accesses the csdev->conns is bounded by the csdev->nr_outport check,
> hence we don't try to dereference the ZERO_SIZE_PTR. This patch cleans
> up the csdev->conns and csdev->refcnt, initialisation to make sure we

This patch no longer deals with csdev->refcnt.



> initialise it properly(i.e, either NULL or valid conns array).
>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  drivers/hwtracing/coresight/coresight.c | 24 ++++++++++++++----------
>  1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
> index 0fdaaf4..49eb749 100644
> --- a/drivers/hwtracing/coresight/coresight.c
> +++ b/drivers/hwtracing/coresight/coresight.c
> @@ -890,7 +890,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>         int nr_refcnts = 1;
>         atomic_t *refcnts = NULL;
>         struct coresight_device *csdev;
> -       struct coresight_connection *conns;
> +       struct coresight_connection *conns = NULL;
>
>         csdev = kzalloc(sizeof(*csdev), GFP_KERNEL);
>         if (!csdev) {
> @@ -918,16 +918,20 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
>
>         csdev->nr_inport = desc->pdata->nr_inport;
>         csdev->nr_outport = desc->pdata->nr_outport;
> -       conns = kcalloc(csdev->nr_outport, sizeof(*conns), GFP_KERNEL);
> -       if (!conns) {
> -               ret = -ENOMEM;
> -               goto err_kzalloc_conns;
> -       }
>
> -       for (i = 0; i < csdev->nr_outport; i++) {
> -               conns[i].outport = desc->pdata->outports[i];
> -               conns[i].child_name = desc->pdata->child_names[i];
> -               conns[i].child_port = desc->pdata->child_ports[i];
> +       /* Initialise connections if there is at least one outport */
> +       if (csdev->nr_outport) {
> +               conns = kcalloc(csdev->nr_outport, sizeof(*conns), GFP_KERNEL);
> +               if (!conns) {
> +                       ret = -ENOMEM;
> +                       goto err_kzalloc_conns;
> +               }
> +
> +               for (i = 0; i < csdev->nr_outport; i++) {
> +                       conns[i].outport = desc->pdata->outports[i];
> +                       conns[i].child_name = desc->pdata->child_names[i];
> +                       conns[i].child_port = desc->pdata->child_ports[i];
> +               }
>         }
>
>         csdev->conns = conns;
> --
> 1.9.1
>