[PATCH] staging: media: lirc: lirc_zilog: Fix for possible null pointer dereference

[PATCH] staging: media: lirc: lirc_zilog: Fix for possible null pointer dereference

[Rickard Strandqvist]

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 <rickard_strandqvist@spectrumdigital.se>
---
 drivers/staging/media/lirc/lirc_zilog.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/staging/media/lirc/lirc_zilog.c b/drivers/staging/media/lirc/lirc_zilog.c
index cc872fb..78ce3b0 100644
--- a/drivers/staging/media/lirc/lirc_zilog.c
+++ b/drivers/staging/media/lirc/lirc_zilog.c
@@ -1332,10 +1332,8 @@ static int close(struct inode *node, struct file *filep)
 	/* find our IR struct */
 	struct IR *ir = filep->private_data;
 
-	if (ir == NULL) {
-		dev_err(ir->l.dev, "close: no private_data attached to the file!\n");
+	if (ir == NULL)
 		return -ENODEV;
-	}
 
 	atomic_dec(&ir->open_count);
 
-- 
1.7.10.4

Re: [PATCH] staging: media: lirc: lirc_zilog: Fix for possible null pointer dereference

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 854 bytes --]

On Thu, 29 Jan 2015 19:48:08 +0100, Rickard Strandqvist said:
> 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 <rickard_strandqvist@spectrumdigital.se>
> ---
>  drivers/staging/media/lirc/lirc_zilog.c |    4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

>  	/* find our IR struct */
>  	struct IR *ir = filep->private_data;
>
> -	if (ir == NULL) {
> -		dev_err(ir->l.dev, "close: no private_data attached to the file!\n");

Yes, the dev_err() call is an obvious thinko.

However, I'm not sure whether removing it entirely is right either.  If
there *should* be a struct IR * passed there, maybe some other printk()
should be issued, or even a WARN_ON(!ir), or something?

[-- Attachment #2: Type: application/pgp-signature, Size: 848 bytes --]

Re: [PATCH] staging: media: lirc: lirc_zilog: Fix for possible null pointer dereference

[Dan Carpenter]

On Thu, Jan 29, 2015 at 05:12:40PM -0500, Valdis.Kletnieks@vt.edu wrote:
> On Thu, 29 Jan 2015 19:48:08 +0100, Rickard Strandqvist said:
> > 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 <rickard_strandqvist@spectrumdigital.se>
> > ---
> >  drivers/staging/media/lirc/lirc_zilog.c |    4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> >  	/* find our IR struct */
> >  	struct IR *ir = filep->private_data;
> >
> > -	if (ir == NULL) {
> > -		dev_err(ir->l.dev, "close: no private_data attached to the file!\n");
> 
> Yes, the dev_err() call is an obvious thinko.
> 
> However, I'm not sure whether removing it entirely is right either.  If
> there *should* be a struct IR * passed there, maybe some other printk()
> should be issued, or even a WARN_ON(!ir), or something?

We set filep->private_data to non-NULL in open() so I don't think it can
be NULL here.

regards,
dan carpenter

Re: [PATCH] staging: media: lirc: lirc_zilog: Fix for possible null pointer dereference

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 647 bytes --]

On Fri, 30 Jan 2015 16:00:02 +0300, Dan Carpenter said:

> > > -	if (ir == NULL) {
> > > -		dev_err(ir->l.dev, "close: no private_data attached to the file
!\n");
> >
> > Yes, the dev_err() call is an obvious thinko.
> >
> > However, I'm not sure whether removing it entirely is right either.  If
> > there *should* be a struct IR * passed there, maybe some other printk()
> > should be issued, or even a WARN_ON(!ir), or something?
>
> We set filep->private_data to non-NULL in open() so I don't think it can
> be NULL here.

Then probably the *right* fix is to remove the *entire* if statement, as
we can't end up doing the 'return -ENODEV'....

[-- Attachment #2: Type: application/pgp-signature, Size: 848 bytes --]

Re: [PATCH] staging: media: lirc: lirc_zilog: Fix for possible null pointer dereference

[Rickard Strandqvist]

2015-01-30 14:09 GMT+01:00  <Valdis.Kletnieks@vt.edu>:
> On Fri, 30 Jan 2015 16:00:02 +0300, Dan Carpenter said:
>
>> > > - if (ir == NULL) {
>> > > -         dev_err(ir->l.dev, "close: no private_data attached to the file
> !\n");
>> >
>> > Yes, the dev_err() call is an obvious thinko.
>> >
>> > However, I'm not sure whether removing it entirely is right either.  If
>> > there *should* be a struct IR * passed there, maybe some other printk()
>> > should be issued, or even a WARN_ON(!ir), or something?
>>
>> We set filep->private_data to non-NULL in open() so I don't think it can
>> be NULL here.
>
> Then probably the *right* fix is to remove the *entire* if statement, as
> we can't end up doing the 'return -ENODEV'....


Hi

Ok, but think or know. Who knows?
Do the remove if patch?


Kind regards
Rickard Strandqvist

Re: [PATCH] staging: media: lirc: lirc_zilog: Fix for possible null pointer dereference

[Andy Walls]

On Fri, 2015-01-30 at 08:09 -0500, Valdis.Kletnieks@vt.edu wrote:
> On Fri, 30 Jan 2015 16:00:02 +0300, Dan Carpenter said:
> 
> > > > -	if (ir == NULL) {
> > > > -		dev_err(ir->l.dev, "close: no private_data attached to the file
> !\n");
> > >

commit be4aa8157c981a8bb9634b886bf1180f97205259
removed the dprintk(), which didn't depend on ir->l.dev, with this
dev_err() call.  That was the wrong thing to do. pr_info() is probably
the right thing to use, if one doesn't have a struct device instance.  

> > > Yes, the dev_err() call is an obvious thinko.
> > >
> > > However, I'm not sure whether removing it entirely is right either.  If
> > > there *should* be a struct IR * passed there, maybe some other printk()
> > > should be issued, or even a WARN_ON(!ir), or something?
> >
> > We set filep->private_data to non-NULL in open() so I don't think it can
> > be NULL here.
> 
> Then probably the *right* fix is to remove the *entire* if statement, as
> we can't end up doing the 'return -ENODEV'....

The if() clause is here as an artifact of being part of a mass port of
lirc drivers from userspace.  I never removed it, because I needed it
when fixing all the lirc_zilog.c ref counting.

IF I got all the lirc_zilog ref counting right, and the upper layers of
the kernel never call close() in error, then this if() statement is not
needed.

I welcome anyone wishing to audit the ref-counting in lirc_zilog.  It
was mentally exhausting to get to what I think is right.  Maybe I just
tire easily mentally though. :)

-Andy