[PATCH 2/2] PCI: endpoint: pci-epf-ntb: Add check to detect 'db_count' value of 0

[Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>]

From: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>

epf_ntb::db_count value should be within 1 to MAX_DB_COUNT. Current code
only checks for the upper bound, while the lower bound is unchecked. This
can cause a lot of issues in the driver if the user passes 'db_count' as 0.

So add a check for 0 also. While at it, remove the redundant 'db_count'
assignment.

Fixes: 8b821cf76150 ("PCI: endpoint: Add EP function driver to provide NTB functionality")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
---
 drivers/pci/endpoint/functions/pci-epf-ntb.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-ntb.c b/drivers/pci/endpoint/functions/pci-epf-ntb.c
index 2bdcc35b652c..7edd177f861f 100644
--- a/drivers/pci/endpoint/functions/pci-epf-ntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-ntb.c
@@ -559,12 +559,15 @@ static int epf_ntb_configure_db(struct epf_ntb *ntb,
 	struct pci_epc *epc;
 	int ret;
 
-	if (db_count > MAX_DB_COUNT)
-		return -EINVAL;
-
 	ntb_epc = ntb->epc[type];
 	epc = ntb_epc->epc;
 
+	if (!db_count || db_count > MAX_DB_COUNT) {
+		dev_err(&epc->dev, "DB count %d out of range (1 - %d)\n",
+			db_count, MAX_DB_COUNT);
+		return -EINVAL;
+	}
+
 	if (msix)
 		ret = epf_ntb_configure_msix(ntb, type, db_count);
 	else
@@ -1297,12 +1300,12 @@ static int epf_ntb_configure_interrupt(struct epf_ntb *ntb,
 	vfunc_no = ntb_epc->vfunc_no;
 
 	db_count = ntb->db_count;
-	if (db_count > MAX_DB_COUNT) {
-		dev_err(dev, "DB count cannot be more than %d\n", MAX_DB_COUNT);
+	if (!db_count || db_count > MAX_DB_COUNT) {
+		dev_err(dev, "DB count %d out of range (1 - %d)\n",
+			db_count, MAX_DB_COUNT);
 		return -EINVAL;
 	}
 
-	ntb->db_count = db_count;
 	epc = ntb_epc->epc;
 
 	if (msi_capable) {
-- 
2.51.0