Re: [PATCH v7 1/6] soc: qcom: pdr: protect locator_addr with the main mutex

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On 4/24/2024 2:27 AM, Dmitry Baryshkov wrote:
If the service locator server is restarted fast enough, the PDR can
rewrite locator_addr fields concurrently. Protect them by placing
modification of those fields under the main pdr->lock.

Fixes: fbe639b44a82 ("soc: qcom: Introduce Protection Domain Restart helpers")
Tested-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx> # on SM8550-QRD
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
  drivers/soc/qcom/pdr_interface.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/qcom/pdr_interface.c b/drivers/soc/qcom/pdr_interface.c
index a1b6a4081dea..19cfe4b41235 100644
--- a/drivers/soc/qcom/pdr_interface.c
+++ b/drivers/soc/qcom/pdr_interface.c
@@ -76,12 +76,12 @@ static int pdr_locator_new_server(struct qmi_handle *qmi,
  					      locator_hdl);
  	struct pdr_service *pds;
+ mutex_lock(&pdr->lock);
  	/* Create a local client port for QMI communication */
  	pdr->locator_addr.sq_family = AF_QIPCRTR;
  	pdr->locator_addr.sq_node = svc->node;
  	pdr->locator_addr.sq_port = svc->port;
- mutex_lock(&pdr->lock);
  	pdr->locator_init_complete = true;
  	mutex_unlock(&pdr->lock);
@@ -104,10 +104,10 @@ static void pdr_locator_del_server(struct qmi_handle *qmi, mutex_lock(&pdr->lock);
  	pdr->locator_init_complete = false;
-	mutex_unlock(&pdr->lock);
pdr->locator_addr.sq_node = 0;
  	pdr->locator_addr.sq_port = 0;
+	mutex_unlock(&pdr->lock);
  }
static const struct qmi_ops pdr_locator_ops = {


These two functions are provided as qmi_ops handlers in pdr_locator_ops. Aren't they serialized in the qmi handle's workqueue since it as an ordered_workqueue? Even in a fast pdr scenario I don't think we would see a race condition between these two functions.

The other access these two functions do race against is in the pdr_notifier_work. I think you would need to protect locator_addr in pdr_get_domain_list since the qmi_send_request there uses 'pdr->locator_addr'.

Thanks!
Chris




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