[media] Zarlink zl10036 DVB-S: Fix mem leak in zl10036_attach

On Thu, 17 Feb 2011, Matthias Schwarzott wrote:

> On Sunday 06 February 2011, Jesper Juhl wrote:
> > If the memory allocation to 'state' succeeds but we jump to the 'error'
> > label before 'state' is assigned to fe->tuner_priv, then the call to
> > 'zl10036_release(fe)' at the 'error:' label will not free 'state', but
> > only what was previously assigned to 'tuner_priv', thus leaking the memory
> > allocated to 'state'.
> > There are may ways to fix this, including assigning the allocated memory
> > directly to 'fe->tuner_priv', but I did not go for that since the
> > additional pointer derefs are more expensive than the local variable, so I
> > just added a 'kfree(state)' call. I guess the call to 'zl10036_release'
> > might not even be needed in this case, but I wasn't sure, so I left it in.
> >
> Yeah, that call to zl10036_release can be completely eleminated.
> Another thing is: jumping to the error label only makes sense when memory was
> already allocated. So the jump in line 471 can be replaced by "return NULL",
> as the other error handling before allocation:
>         if (NULL == config) {
>                 printk(KERN_ERR "%s: no config specified", __func__);
>                 goto error;
>         }
>
> I suggest to improve the patch to clean the code up when changing that.
>
> But I am fine with commiting this patch also if you do not want to change it.
>

Thank you for your feedback. It makes a lot of sense.
Changing it is not a problem :)
How about the updated patch below?

If the memory allocation to 'state' succeeds but we jump to the 'error'
label before 'state' is assigned to fe->tuner_priv, then the call to
'zl10036_release(fe)' at the 'error:' label will not free 'state', but
only what was previously assigned to 'tuner_priv', thus leaking the memory
allocated to 'state'.
This patch fixes the leak and also does not jump to 'error:' before mem
has been allocated but instead just returns. Also some small style
cleanups.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/frontends/zl10036.c

@@ -463,16 +463,16 @@ struct dvb_frontend *zl10036_attach(struct dvb_frontend *fe,
 				    const struct zl10036_config *config,
 				    struct i2c_adapter *i2c)
 {
-	struct zl10036_state *state = NULL;
+	struct zl10036_state *state;
 	int ret;
 
-	if (NULL == config) {
+	if (!config) {
 		printk(KERN_ERR "%s: no config specified", __func__);
-		goto error;
+		return NULL;
 	}
 
 	state = kzalloc(sizeof(struct zl10036_state), GFP_KERNEL);
-	if (NULL == state)
+	if (!state)
 		return NULL;
 
 	state->config = config;
@@ -507,7 +507,7 @@ struct dvb_frontend *zl10036_attach(struct dvb_frontend *fe,
 	return fe;
 
 error:
-	zl10036_release(fe);
+	kfree(state);
 	return NULL;
 }
 EXPORT_SYMBOL(zl10036_attach);