netdev - [PATCH net-next v3] net: thunderx: Fix format-truncation warning in bgx_acpi_match

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Message-ID: <20250711140532.2463602-1-alok.a.tiwari@oracle.com>
Date: Fri, 11 Jul 2025 07:05:30 -0700
From: Alok Tiwari <alok.a.tiwari@...cle.com>
To: sgoutham@...vell.com, andrew+netdev@...n.ch, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        horms@...nel.org, netdev@...r.kernel.org
Cc: alok.a.tiwari@...cle.com, linux-arm-kernel@...ts.infradead.org,
        darren.kenny@...cle.com, linux-kernel@...r.kernel.org
Subject: [PATCH net-next v3] net: thunderx: Fix format-truncation warning in bgx_acpi_match_id()

The buffer bgx_sel used in snprintf() was too small to safely hold
the formatted string "BGX%d" for all valid bgx_id values. This caused
a -Wformat-truncation warning with `Werror` enabled during build.

Increase the buffer size from 5 to 7 and use `sizeof(bgx_sel)` in
snprintf() to ensure safety and suppress the warning.

Build warning:
  CC      drivers/net/ethernet/cavium/thunder/thunder_bgx.o
  drivers/net/ethernet/cavium/thunder/thunder_bgx.c: In function
‘bgx_acpi_match_id’:
  drivers/net/ethernet/cavium/thunder/thunder_bgx.c:1434:27: error: ‘%d’
directive output may be truncated writing between 1 and 3 bytes into a
region of size 2 [-Werror=format-truncation=]
    snprintf(bgx_sel, 5, "BGX%d", bgx->bgx_id);
                             ^~
  drivers/net/ethernet/cavium/thunder/thunder_bgx.c:1434:23: note:
directive argument in the range [0, 255]
    snprintf(bgx_sel, 5, "BGX%d", bgx->bgx_id);
                         ^~~~~~~
  drivers/net/ethernet/cavium/thunder/thunder_bgx.c:1434:2: note:
‘snprintf’ output between 5 and 7 bytes into a destination of size 5
    snprintf(bgx_sel, 5, "BGX%d", bgx->bgx_id);

compiler warning due to insufficient snprintf buffer size.

Signed-off-by: Alok Tiwari <alok.a.tiwari@...cle.com>
Reviewed-by: Simon Horman <horms@...nel.org>
---
v2->v3
added Reviewed-by: Simon
used bgx_sel[7] as suggested by Jakub Kicinski
https://lore.kernel.org/all/20250710153422.6adae255@kernel.org/
v1->v2
No changes. Targeting for net-next.
https://lore.kernel.org/all/20250708160957.GQ452973@horms.kernel.org/
---
 drivers/net/ethernet/cavium/thunder/thunder_bgx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cavium/thunder/thunder_bgx.c b/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
index 3b7ad744b2dd6..21495b5dce254 100644
--- a/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
+++ b/drivers/net/ethernet/cavium/thunder/thunder_bgx.c
@@ -1429,9 +1429,9 @@ static acpi_status bgx_acpi_match_id(acpi_handle handle, u32 lvl,
 {
 	struct acpi_buffer string = { ACPI_ALLOCATE_BUFFER, NULL };
 	struct bgx *bgx = context;
-	char bgx_sel[5];
+	char bgx_sel[7];
 
-	snprintf(bgx_sel, 5, "BGX%d", bgx->bgx_id);
+	snprintf(bgx_sel, sizeof(bgx_sel), "BGX%d", bgx->bgx_id);
 	if (ACPI_FAILURE(acpi_get_name(handle, ACPI_SINGLE_NAME, &string))) {
 		pr_warn("Invalid link device\n");
 		return AE_OK;
-- 
2.46.0