linux-kernel - Re: [PATCH 2/2] s390: Fix possibly wrong size in strncmp (smsglucv)

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Date:	Sun, 30 Jan 2011 13:01:55 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Stefan Weil <stefan@...lnetz.de>
Cc:	Jesper Juhl <jj@...osbits.net>, linux390@...ibm.com,
	Ursula Braun <ursula.braun@...ibm.com>,
	Frank Blaschka <blaschka@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] s390: Fix possibly wrong size in strncmp (smsglucv)

On Sun, Jan 30, 2011 at 00:00, Stefan Weil <stefan@...lnetz.de> wrote:
> Am 29.01.2011 22:38, schrieb Jesper Juhl:
>> On Sat, 29 Jan 2011, Stefan Weil wrote:
>>> This error was reported by cppcheck:
>>> drivers/s390/net/smsgiucv.c:63: error: Using sizeof for array given as
>>> function argument returns the size of pointer.
>>>
>>> Although there is no runtime problem as long as sizeof(u8 *) == 8,
>>> this misleading code should get fixed.
>>>
>>> Cc: Ursula Braun<ursula.braun@...ibm.com>
>>> Cc: linux390@...ibm.com
>>> Cc: Frank Blaschka<blaschka@...ux.vnet.ibm.com>
>>> Cc: Martin Schwidefsky<schwidefsky@...ibm.com>
>>> Cc: Heiko Carstens<heiko.carstens@...ibm.com>
>>> Cc: linux-s390@...r.kernel.org
>>> Cc: linux-kernel@...r.kernel.org
>>> Signed-off-by: Stefan Weil<weil@...l.berlios.de>
>>> ---
>>>  drivers/s390/net/smsgiucv.c |    2 +-
>>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/drivers/s390/net/smsgiucv.c b/drivers/s390/net/smsgiucv.c
>>> index 65e1cf1..207b7d7 100644
>>> --- a/drivers/s390/net/smsgiucv.c
>>> +++ b/drivers/s390/net/smsgiucv.c
>>> @@ -60,7 +60,7 @@ static struct iucv_handler smsg_handler = {
>>>  static int smsg_path_pending(struct iucv_path *path, u8 ipvmid[8],
>>>                             u8 ipuser[16])
>>>  {
>>> -       if (strncmp(ipvmid, "*MSG    ", sizeof(ipvmid)) != 0)
>>> +       if (strncmp(ipvmid, "*MSG    ", 8) != 0)
>>>
>>
>> Hmm, shouldn't this really be  ARRAY_SIZE(ipvmid)  ??
>>
>
> I think that would be wrong, too (only in this special case where
> an array is passed as a function parameter).

Yeah, I got b itten by that recently as well:

if `u8 ipvmid[8]' is a variable, `sizeof(ipvmid) == 8'.
If it's a function parameter, `sizeof(ipvmid) == sizeof(void *)'.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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