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    SubjectRe: [PATCH v2 4/9] coresight: Fix csdev connections initialisation
    On 6 June 2016 at 03:11, Suzuki K Poulose <suzuki.poulose@arm.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@linaro.org>
    > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.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
    >

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