2015-02-02 16:36:49

by Sudip Mukherjee

Subject: Re: [PATCH] staging: gdm724x: gdm_tty: Fix for possible null pointer dereference

On Thu, Jan 29, 2015 at 07:46:10PM +0100, Rickard Strandqvist wrote:
> Fix a possible null pointer dereference, there is
> otherwise a risk of a possible null pointer dereference.
>
> This was found using a static code analysis program called cppcheck
>
> Signed-off-by: Rickard Strandqvist <[email protected]>
> ---
> drivers/staging/gdm724x/gdm_tty.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/staging/gdm724x/gdm_tty.c b/drivers/staging/gdm724x/gdm_tty.c
> index 001348c..66b356e 100644
> --- a/drivers/staging/gdm724x/gdm_tty.c
> +++ b/drivers/staging/gdm724x/gdm_tty.c
> @@ -145,7 +145,7 @@ static int gdm_tty_recv_complete(void *data,
> struct gdm *gdm = tty_dev->gdm[index];
>
> if (!GDM_TTY_READY(gdm)) {
> - if (complete == RECV_PACKET_PROCESS_COMPLETE)
> + if (gdm && complete == RECV_PACKET_PROCESS_COMPLETE)
GDM_TTY_READY() is already checking for gdm, there is no chance that gdm can be null at this point. so this additional check is not required.

regards
sudip
> gdm_tty_recv(gdm, gdm_tty_recv_complete);
> return TO_HOST_PORT_CLOSE;
> }
> --
> 1.7.10.4
>
> --
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> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/

2015-02-04 17:46:37

by Rickard Strandqvist

Subject: Re: [PATCH] staging: gdm724x: gdm_tty: Fix for possible null pointer dereference

2015-02-02 17:36 GMT+01:00 Sudip Mukherjee <[email protected]>:
> On Thu, Jan 29, 2015 at 07:46:10PM +0100, Rickard Strandqvist wrote:
>> Fix a possible null pointer dereference, there is
>> otherwise a risk of a possible null pointer dereference.
>>
>> This was found using a static code analysis program called cppcheck
>>
>> Signed-off-by: Rickard Strandqvist <[email protected]>
>> ---
>> drivers/staging/gdm724x/gdm_tty.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/staging/gdm724x/gdm_tty.c b/drivers/staging/gdm724x/gdm_tty.c
>> index 001348c..66b356e 100644
>> --- a/drivers/staging/gdm724x/gdm_tty.c
>> +++ b/drivers/staging/gdm724x/gdm_tty.c
>> @@ -145,7 +145,7 @@ static int gdm_tty_recv_complete(void *data,
>> struct gdm *gdm = tty_dev->gdm[index];
>>
>> if (!GDM_TTY_READY(gdm)) {
>> - if (complete == RECV_PACKET_PROCESS_COMPLETE)
>> + if (gdm && complete == RECV_PACKET_PROCESS_COMPLETE)
> GDM_TTY_READY() is already checking for gdm, there is no chance that gdm can be null at this point. so this additional check is not required.
>
> regards
> sudip
>> gdm_tty_recv(gdm, gdm_tty_recv_complete);
>> return TO_HOST_PORT_CLOSE;
>> }
>> --
>> 1.7.10.4
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to [email protected]
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/


Hi Sudip

Yes, GDM_TTY_READY checks gdm, but this is a if(! )


Kind regards
Rickard Strandqvist

2015-02-05 12:19:30

by Dan Carpenter

Subject: Re: [PATCH] staging: gdm724x: gdm_tty: Fix for possible null pointer dereference

On Wed, Feb 04, 2015 at 06:46:34PM +0100, Rickard Strandqvist wrote:
> 2015-02-02 17:36 GMT+01:00 Sudip Mukherjee <[email protected]>:
> > On Thu, Jan 29, 2015 at 07:46:10PM +0100, Rickard Strandqvist wrote:
> >> diff --git a/drivers/staging/gdm724x/gdm_tty.c b/drivers/staging/gdm724x/gdm_tty.c
> >> index 001348c..66b356e 100644
> >> --- a/drivers/staging/gdm724x/gdm_tty.c
> >> +++ b/drivers/staging/gdm724x/gdm_tty.c
> >> @@ -145,7 +145,7 @@ static int gdm_tty_recv_complete(void *data,
> >> struct gdm *gdm = tty_dev->gdm[index];
> >>
> >> if (!GDM_TTY_READY(gdm)) {
> >> - if (complete == RECV_PACKET_PROCESS_COMPLETE)
> >> + if (gdm && complete == RECV_PACKET_PROCESS_COMPLETE)
> > GDM_TTY_READY() is already checking for gdm, there is no chance that gdm can be null at this point. so this additional check is not required.
> >
> > regards
> > sudip
> >> gdm_tty_recv(gdm, gdm_tty_recv_complete);
> >> return TO_HOST_PORT_CLOSE;
> >> }
>
> Hi Sudip
>
> Yes, GDM_TTY_READY checks gdm, but this is a if(! )
>

You're right. But, by that same logic, we should also test
gdm->tty_dev. So it looks like this:

if (!GDM_TTY_READY(gdm)) {
if (gdm && gdm->tty_dev && complete == RECV_PACKET_PROCESS_COMPLETE)
gdm_tty_recv(gdm, gdm_tty_recv_complete);
return TO_HOST_PORT_CLOSE;
}

That is really sucky... Garbage code like this is why kernel style
doesn't favour macros. We should just open code GDM_TTY_READY() and
gdm_tty_recv() so that people can read the code.

I wonder if "gdm->tty_dev" is the same as the "tty_dev" parameter?

regards,
dan carpenter