[PATCH v1 1/1] leds: pca955x: Avoid potential overflow when filling default_label (take 2)

[PATCH v1 1/1] leds: pca955x: Avoid potential overflow when filling default_label (take 2)

[Andy Shevchenko]

GCC compiler v8.5.0 is not happy about printing
into a too short buffer (when build with `make W=1`):

  drivers/leds/leds-pca955x.c:696:5: note: 'snprintf' output between 2 and 11 bytes into a destination of size 8

Unfortunately this is a false positive from the old GCC versions,
but we may still improve the code by using '%hhu' format specifier
and reduce buffer size by 4 bytes.

Fixes: bd3d14932923 ("leds: pca955x: Avoid potential overflow when filling default_label")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506282159.TXfvorYl-lkp@intel.com/
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/leds/leds-pca955x.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index 42fe056b1c74..70d109246088 100644
--- a/drivers/leds/leds-pca955x.c
+++ b/drivers/leds/leds-pca955x.c
@@ -587,7 +587,7 @@ static int pca955x_probe(struct i2c_client *client)
 	struct pca955x_platform_data *pdata;
 	bool keep_psc0 = false;
 	bool set_default_label = false;
-	char default_label[8];
+	char default_label[4];
 	int bit, err, reg;
 
 	chip = i2c_get_match_data(client);
@@ -693,7 +693,7 @@ static int pca955x_probe(struct i2c_client *client)
 			}
 
 			if (set_default_label) {
-				snprintf(default_label, sizeof(default_label), "%u", i);
+				snprintf(default_label, sizeof(default_label), "%hhu", i);
 				init_data.default_label = default_label;
 			} else {
 				init_data.default_label = NULL;
-- 
2.47.2

Re: (subset) [PATCH v1 1/1] leds: pca955x: Avoid potential overflow when filling default_label (take 2)

[Lee Jones]

On Mon, 30 Jun 2025 12:39:06 +0300, Andy Shevchenko wrote:
> GCC compiler v8.5.0 is not happy about printing
> into a too short buffer (when build with `make W=1`):
> 
>   drivers/leds/leds-pca955x.c:696:5: note: 'snprintf' output between 2 and 11 bytes into a destination of size 8
> 
> Unfortunately this is a false positive from the old GCC versions,
> but we may still improve the code by using '%hhu' format specifier
> and reduce buffer size by 4 bytes.
> 
> [...]

Applied, thanks!

[1/1] leds: pca955x: Avoid potential overflow when filling default_label (take 2)
      commit: 239afba8b9f3b0fcfd464d5ffeaed0ed4441c5a4

--
Lee Jones [李琼斯]