linux-kernel - [PATCH 5/9] surface3_power: avoid format string truncation warning

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Date: Tue, 26 Mar 2024 23:38:04 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: llvm@...ts.linux.dev,
	Hans de Goede <hdegoede@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Maximilian Luz <luzmaximilian@...il.com>,
	Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	platform-driver-x86@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 5/9] surface3_power: avoid format string truncation warning

From: Arnd Bergmann <arnd@...db.de>

clang warns about printing a pair of escaped strings into a buffer that is
too short:

drivers/platform/surface/surface3_power.c:248:3: error: 'snprintf' will always be truncated; specified size is 10, but format string expands to at least 12 [-Werror,-Wformat-truncation-non-kprintf]
  248 |                 snprintf(bix->serial, ARRAY_SIZE(bix->serial), "%3pE%6pE", buf + 7, buf);
      |                 ^

Change the format string two print two less bytes so it always fits. The string
is still truncated, so there is no change in behavior, but the compiler no
longer warns about it.

Fixes: 85f7582cd484 ("platform/surface: Move Surface 3 Power OpRegion driver to platform/surface")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Not entirely sure about this one, as I've never used escaped strings, and
don't know if gcc is correct to warn here, or if the kernel defines it
differently from the standard.
---
 drivers/platform/surface/surface3_power.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/surface/surface3_power.c b/drivers/platform/surface/surface3_power.c
index 4c0f92562a79..72f904761fde 100644
--- a/drivers/platform/surface/surface3_power.c
+++ b/drivers/platform/surface/surface3_power.c
@@ -245,7 +245,7 @@ static int mshw0011_bix(struct mshw0011_data *cdata, struct bix *bix)
 		dev_err(&client->dev, "Error reading serial no: %d\n", ret);
 		return ret;
 	} else {
-		snprintf(bix->serial, ARRAY_SIZE(bix->serial), "%3pE%6pE", buf + 7, buf);
+		snprintf(bix->serial, ARRAY_SIZE(bix->serial), "%3pE%4pE", buf + 7, buf);
 	}
 
 	/* get cycle count */
-- 
2.39.2