[RFC,1/6] net: rfkill: gpio: fix gpio name buffer size off by 1
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Message ID 1389941251-32692-2-git-send-email-wens@csie.org
State New, archived
Headers show

Commit Message

Chen-Yu Tsai (Moxa) Jan. 17, 2014, 6:47 a.m. UTC
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.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
 net/rfkill/rfkill-gpio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

David Laight Jan. 17, 2014, 9:46 a.m. UTC | #1
From: Chen-Yu Tsai
> 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.
...
> diff --git a/net/rfkill/rfkill-gpio.c b/net/rfkill/rfkill-gpio.c
...
> -	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.

	David
Chen-Yu Tsai (Moxa) Jan. 17, 2014, 9:59 a.m. UTC | #2
On Fri, Jan 17, 2014 at 5:46 PM, David Laight <David.Laight@aculab.com> wrote:
> From: Chen-Yu Tsai
>> 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.
> ...
>> diff --git a/net/rfkill/rfkill-gpio.c b/net/rfkill/rfkill-gpio.c
> ...
>> -     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

Patch
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diff --git a/net/rfkill/rfkill-gpio.c b/net/rfkill/rfkill-gpio.c
index bd2a5b9..97ec12a 100644
--- a/net/rfkill/rfkill-gpio.c
+++ b/net/rfkill/rfkill-gpio.c
@@ -117,8 +117,8 @@  static int rfkill_gpio_probe(struct platform_device *pdev)
 	if (!rfkill->shutdown_name)
 		return -ENOMEM;
 
-	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);
 
 	rfkill->clk = devm_clk_get(&pdev->dev, clk_name);