[RFC PATCH v2 01/27] PCI: endpoint: pci-epf-vntb: Use array_index_nospec() on mws_size[] access

[Koichiro Den]

Follow common kernel idioms for indices derived from configfs attributes
and suppress Smatch warnings:

  epf_ntb_mw1_show() warn: potential spectre issue 'ntb->mws_size' [r]
  epf_ntb_mw1_store() warn: potential spectre issue 'ntb->mws_size' [w]

Also fix the error message for out-of-range MW indices.

Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
 drivers/pci/endpoint/functions/pci-epf-vntb.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 3ecc5059f92b..6c4c78915970 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -995,17 +995,18 @@ static ssize_t epf_ntb_##_name##_show(struct config_item *item,		\
 	struct config_group *group = to_config_group(item);		\
 	struct epf_ntb *ntb = to_epf_ntb(group);			\
 	struct device *dev = &ntb->epf->dev;				\
-	int win_no;							\
+	int win_no, idx;						\
 									\
 	if (sscanf(#_name, "mw%d", &win_no) != 1)			\
 		return -EINVAL;						\
 									\
 	if (win_no <= 0 || win_no > ntb->num_mws) {			\
-		dev_err(dev, "Invalid num_nws: %d value\n", ntb->num_mws); \
+		dev_err(dev, "MW%d out of range (num_mws=%d)\n",	\
+			win_no, ntb->num_mws);				\
 		return -EINVAL;						\
 	}								\
-									\
-	return sprintf(page, "%lld\n", ntb->mws_size[win_no - 1]);	\
+	idx = array_index_nospec(win_no - 1, ntb->num_mws);		\
+	return sprintf(page, "%lld\n", ntb->mws_size[idx]);		\
 }
 
 #define EPF_NTB_MW_W(_name)						\
@@ -1015,7 +1016,7 @@ static ssize_t epf_ntb_##_name##_store(struct config_item *item,	\
 	struct config_group *group = to_config_group(item);		\
 	struct epf_ntb *ntb = to_epf_ntb(group);			\
 	struct device *dev = &ntb->epf->dev;				\
-	int win_no;							\
+	int win_no, idx;						\
 	u64 val;							\
 	int ret;							\
 									\
@@ -1027,11 +1028,13 @@ static ssize_t epf_ntb_##_name##_store(struct config_item *item,	\
 		return -EINVAL;						\
 									\
 	if (win_no <= 0 || win_no > ntb->num_mws) {			\
-		dev_err(dev, "Invalid num_nws: %d value\n", ntb->num_mws); \
+		dev_err(dev, "MW%d out of range (num_mws=%d)\n",	\
+			win_no, ntb->num_mws);				\
 		return -EINVAL;						\
 	}								\
 									\
-	ntb->mws_size[win_no - 1] = val;				\
+	idx = array_index_nospec(win_no - 1, ntb->num_mws);		\
+	ntb->mws_size[idx] = val;					\
 									\
 	return len;							\
 }
-- 
2.48.1