diff mbox

av7110: make array offset unsigned

Message ID 20110106194059.GC1717@bicker (mailing list archive)
State Superseded, archived
Headers

Commit Message

Dan Carpenter Jan. 6, 2011, 7:41 p.m. UTC 
  In the CA_GET_SLOT_INFO ioctl, we only check whether "num" is too large,
but we don't check if it's negative.

drivers/media/dvb/ttpci/av7110_ca.c
   278		ca_slot_info_t *info=(ca_slot_info_t *)parg;
   279
   280		if (info->num > 1)
   281			return -EINVAL;
   282		av7110->ci_slot[info->num].num = info->num;

Let's just make it unsigned.

Signed-off-by: Dan Carpenter <error27@gmail.com>
---
Compile tested.

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Comments

Andreas Oberritter Jan. 7, 2011, 12:44 p.m. UTC | #1 
On 01/06/2011 08:41 PM, Dan Carpenter wrote:
> In the CA_GET_SLOT_INFO ioctl, we only check whether "num" is too large,
> but we don't check if it's negative.
> 
> drivers/media/dvb/ttpci/av7110_ca.c
>    278		ca_slot_info_t *info=(ca_slot_info_t *)parg;
>    279
>    280		if (info->num > 1)
>    281			return -EINVAL;
>    282		av7110->ci_slot[info->num].num = info->num;
> 
> Let's just make it unsigned.
> 
> Signed-off-by: Dan Carpenter <error27@gmail.com>

Nack. You're changing an interface to userspace. Please add a check to
av7110_ca.c instead.

Regards,
Andreas
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Dan Carpenter Jan. 7, 2011, 1:51 p.m. UTC | #2 
On Fri, Jan 07, 2011 at 01:44:15PM +0100, Andreas Oberritter wrote:
> Nack. You're changing an interface to userspace. Please add a check to
> av7110_ca.c instead.
> 

Ok.  I've done that and resent the patch.

But just for my own understanding, why is it wrong to change an int to
an unsigned int in the userspace API?  Who would notice?  (I'm still
quite a newbie at system programming).

regards,
dan carpenter

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Kulikov Vasiliy Jan. 7, 2011, 2:02 p.m. UTC | #3 
On Fri, Jan 07, 2011 at 16:51 +0300, Dan Carpenter wrote:
> But just for my own understanding, why is it wrong to change an int to
> an unsigned int in the userspace API?  Who would notice?

E.g. the same check in userspace (var < 0).  If var has changed the sign
then the result would differ.
Andreas Oberritter Jan. 7, 2011, 2:05 p.m. UTC | #4 
On 01/07/2011 02:51 PM, Dan Carpenter wrote:
> On Fri, Jan 07, 2011 at 01:44:15PM +0100, Andreas Oberritter wrote:
>> Nack. You're changing an interface to userspace. Please add a check to
>> av7110_ca.c instead.
>>
> 
> Ok.  I've done that and resent the patch.

Thanks. I'm OK with the patch, but I'll leave it to the maintainer of
av7110 to decide whether he likes the cast or prefers an additional
signed compare. I added him to CC.

> But just for my own understanding, why is it wrong to change an int to
> an unsigned int in the userspace API?  Who would notice?  (I'm still
> quite a newbie at system programming).

It would generate compiler warnings in userspace for programs checking
for values < 0 or assigning negative values (for whatever reason).

Regards,
Andreas
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diff mbox

Patch

diff --git a/include/linux/dvb/ca.h b/include/linux/dvb/ca.h
index c18537f..647015e 100644
--- a/include/linux/dvb/ca.h
+++ b/include/linux/dvb/ca.h
@@ -27,7 +27,7 @@ 
 /* slot interface types and info */
 
 typedef struct ca_slot_info {
-	int num;               /* slot number */
+	unsigned int num;      /* slot number */
 
 	int type;              /* CA interface this slot supports */
 #define CA_CI            1     /* CI high level interface */