On Fri, Jan 17, 2014 at 5:46 PM, David Laight [off-list ref] wrote:

From: Chen-Yu Tsai

quoted

snprintf should be passed the complete size of the buffer, including
the space for '\0'. The previous code resulted in the *_reset and
*_shutdown strings being truncated.

...

quoted

diff --git a/net/rfkill/rfkill-gpio.c b/net/rfkill/rfkill-gpio.c

...

quoted

-     snprintf(rfkill->reset_name, len + 6 , "%s_reset", rfkill->name);
-     snprintf(rfkill->shutdown_name, len + 9, "%s_shutdown", rfkill->name);
+     snprintf(rfkill->reset_name, len + 7 , "%s_reset", rfkill->name);
+     snprintf(rfkill->shutdown_name, len + 10, "%s_shutdown", rfkill->name);

I can't find the context for the above, but they look very dubious.
I'd expect: snprintf(foo, sizeof foo, ...).
If you are trying to truncate rfkill->name you need to use %.*s.

The driver allocates these buffers on the fly, a few lines above:

        len = strlen(rfkill->name);
        rfkill->reset_name = devm_kzalloc(&pdev->dev, len + 7, GFP_KERNEL);
        rfkill->shutdown_name = devm_kzalloc(&pdev->dev, len + 10, GFP_KERNEL);

I am not trying to truncate rfkill->name. Rather, the buffer length passed
to snprintf was wrong, so the resulting name was truncated by one character.


Thanks,
ChenYu