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

From: Mathieu Poirier
Date: Sun Jun 12 2016 - 16:39:31 EST


On 6 June 2016 at 03:11, Suzuki K Poulose <suzuki.poulose@xxxxxxx> 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@xxxxxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> 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
>