linux-kernel - [PATCH] PCI: endpoint: pci-epf-vntb: Use array_index_nospec() on mws

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Message-ID: <20260105075606.1253697-1-den@valinux.co.jp>
Date: Mon,  5 Jan 2026 16:56:06 +0900
From: Koichiro Den <den@...inux.co.jp>
To: jdmason@...zu.us,
	dave.jiang@...el.com,
	allenbh@...il.com,
	mani@...nel.org,
	kwilczynski@...nel.org,
	kishon@...nel.org,
	bhelgaas@...gle.com
Cc: ntb@...ts.linux.dev,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] PCI: endpoint: pci-epf-vntb: Use array_index_nospec() on mws_size[] access

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 and %lld format
for unsigned values.

Reviewed-by: Frank Li <Frank.Li@....com>
Signed-off-by: Koichiro Den <den@...inux.co.jp>
---
Base: https://github.com/jonmason/ntb/commit/68113d260674 (ntb-next)
This is a spin-off patch from the following series:
https://lore.kernel.org/all/20251217151609.3162665-2-den@valinux.co.jp/

 drivers/pci/endpoint/functions/pci-epf-vntb.c | 24 +++++++++++--------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 83e9ab10f9c4..192dd4f4de8d 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -876,17 +876,19 @@ 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); \
+	idx = win_no - 1;						\
+	if (idx < 0 || idx >= 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(idx, ntb->num_mws);			\
+	return sprintf(page, "%llu\n", ntb->mws_size[idx]);		\
 }
 
 #define EPF_NTB_MW_W(_name)						\
@@ -896,7 +898,7 @@ 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;							\
 									\
@@ -907,12 +909,14 @@ static ssize_t epf_ntb_##_name##_store(struct config_item *item,	\
 	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); \
+	idx = win_no - 1;						\
+	if (idx < 0 || idx >= 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(idx, ntb->num_mws);			\
+	ntb->mws_size[idx] = val;					\
 									\
 	return len;							\
 }
-- 
2.51.0