[PATCH] clk: fix a missing-free bug in clk_cpy_name()

[PATCH] clk: fix a missing-free bug in clk_cpy_name()

[Gen Zhang]

In clk_cpy_name(), '*dst_p'('parent->name'and 'parent->fw_name') and 
'dst' are allcoted by kstrdup_const(). According to doc: "Strings 
allocated by kstrdup_const should be freed by kfree_const". So 
'parent->name', 'parent->fw_name' and 'dst' should be freed.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
---
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index aa51756..85c4d3f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3435,6 +3435,7 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
 	if (!dst)
 		return -ENOMEM;
 
+	kfree_const(dst);
 	return 0;
 }
 
@@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
 				kfree_const(parents[i].name);
 				kfree_const(parents[i].fw_name);
 			} while (--i >= 0);
+			kfree_const(parent->name);
+			kfree_const(parent->fw_name);
 			kfree(parents);
 
 			return ret;
---

Re: [PATCH] clk: fix a missing-free bug in clk_cpy_name()

[Jiri Slaby]

On 31. 05. 19, 3:14, Gen Zhang wrote:
> In clk_cpy_name(), '*dst_p'('parent->name'and 'parent->fw_name') and 
> 'dst' are allcoted by kstrdup_const(). According to doc: "Strings 
> allocated by kstrdup_const should be freed by kfree_const". So 
> 'parent->name', 'parent->fw_name' and 'dst' should be freed.
> 
> Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> ---
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index aa51756..85c4d3f 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3435,6 +3435,7 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
>  	if (!dst)
>  		return -ENOMEM;
>  
> +	kfree_const(dst);

So you are now returning a freed pointer in dst_p?

>  	return 0;
>  }
>  
> @@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
>  				kfree_const(parents[i].name);
>  				kfree_const(parents[i].fw_name);
>  			} while (--i >= 0);
> +			kfree_const(parent->name);
> +			kfree_const(parent->fw_name);

Both of them were just freed in the loop above, no?

thanks,
-- 
js
suse labs

Re: [PATCH] clk: fix a missing-free bug in clk_cpy_name()

[Gen Zhang]

On Wed, Jun 05, 2019 at 08:38:00AM +0200, Jiri Slaby wrote:
> On 31. 05. 19, 3:14, Gen Zhang wrote:
> > In clk_cpy_name(), '*dst_p'('parent->name'and 'parent->fw_name') and 
> > 'dst' are allcoted by kstrdup_const(). According to doc: "Strings 
> > allocated by kstrdup_const should be freed by kfree_const". So 
> > 'parent->name', 'parent->fw_name' and 'dst' should be freed.
> > 
> > Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> > ---
> > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > index aa51756..85c4d3f 100644
> > --- a/drivers/clk/clk.c
> > +++ b/drivers/clk/clk.c
> > @@ -3435,6 +3435,7 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
> >  	if (!dst)
> >  		return -ENOMEM;
> >  
> > +	kfree_const(dst);
> 
> So you are now returning a freed pointer in dst_p?
Thanks for your reply. I re-examined the code, and this kfree is 
incorrect and it should be deleted.
> 
> >  	return 0;
> >  }
> >  
> > @@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
> >  				kfree_const(parents[i].name);
> >  				kfree_const(parents[i].fw_name);
> >  			} while (--i >= 0);
> > +			kfree_const(parent->name);
> > +			kfree_const(parent->fw_name);
> 
> Both of them were just freed in the loop above, no?
for (i = 0, parent = parents; i < num_parents; i++, parent++)
Is 'parent' the same as the one from the loop above?

Moreover, should 'parents[i].name' and 'parents[i].fw_name' be freed by
kfree_const()?

Thanks
Gen
> 
> thanks,
> -- 
> js
> suse labs

Re: [PATCH] clk: fix a missing-free bug in clk_cpy_name()

[Stephen Boyd]

Quoting Gen Zhang (2019-06-05 09:00:43)
> On Wed, Jun 05, 2019 at 08:38:00AM +0200, Jiri Slaby wrote:
> > On 31. 05. 19, 3:14, Gen Zhang wrote:
> > > In clk_cpy_name(), '*dst_p'('parent->name'and 'parent->fw_name') and 
> > > 'dst' are allcoted by kstrdup_const(). According to doc: "Strings 
> > > allocated by kstrdup_const should be freed by kfree_const". So 
> > > 'parent->name', 'parent->fw_name' and 'dst' should be freed.
> > > 
> > > Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> > > ---
> > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > > index aa51756..85c4d3f 100644
> > > --- a/drivers/clk/clk.c
> > > +++ b/drivers/clk/clk.c
> > > @@ -3435,6 +3435,7 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
> > >     if (!dst)
> > >             return -ENOMEM;
> > >  
> > > +   kfree_const(dst);
> > 
> > So you are now returning a freed pointer in dst_p?
> Thanks for your reply. I re-examined the code, and this kfree is 
> incorrect and it should be deleted.
> > 
> > >     return 0;
> > >  }
> > >  
> > > @@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
> > >                             kfree_const(parents[i].name);
> > >                             kfree_const(parents[i].fw_name);
> > >                     } while (--i >= 0);
> > > +                   kfree_const(parent->name);
> > > +                   kfree_const(parent->fw_name);
> > 
> > Both of them were just freed in the loop above, no?
> for (i = 0, parent = parents; i < num_parents; i++, parent++)
> Is 'parent' the same as the one from the loop above?

Yes. Did it change somehow?

> 
> Moreover, should 'parents[i].name' and 'parents[i].fw_name' be freed by
> kfree_const()?
> 

Yes? They're allocated with kstrdup_const() in clk_cpy_name(), or
they're NULL by virtue of the kcalloc and then kfree_const() does
nothing.

I'm having a hard time following what this patch is trying to fix. It
looks unnecessary though so I'm going to drop it from the clk review
queue.

Re: [PATCH] clk: fix a missing-free bug in clk_cpy_name()

[Gen Zhang]

On Thu, Jun 06, 2019 at 01:16:45PM -0700, Stephen Boyd wrote:
> Quoting Gen Zhang (2019-06-05 09:00:43)
> > On Wed, Jun 05, 2019 at 08:38:00AM +0200, Jiri Slaby wrote:
> > > On 31. 05. 19, 3:14, Gen Zhang wrote:
> > > > In clk_cpy_name(), '*dst_p'('parent->name'and 'parent->fw_name') and 
> > > > 'dst' are allcoted by kstrdup_const(). According to doc: "Strings 
> > > > allocated by kstrdup_const should be freed by kfree_const". So 
> > > > 'parent->name', 'parent->fw_name' and 'dst' should be freed.
> > > > 
> > > > Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> > > > ---
> > > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > > > index aa51756..85c4d3f 100644
> > > > --- a/drivers/clk/clk.c
> > > > +++ b/drivers/clk/clk.c
> > > > @@ -3435,6 +3435,7 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
> > > >     if (!dst)
> > > >             return -ENOMEM;
> > > >  
> > > > +   kfree_const(dst);
> > > 
> > > So you are now returning a freed pointer in dst_p?
> > Thanks for your reply. I re-examined the code, and this kfree is 
> > incorrect and it should be deleted.
> > > 
> > > >     return 0;
> > > >  }
> > > >  
> > > > @@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
> > > >                             kfree_const(parents[i].name);
> > > >                             kfree_const(parents[i].fw_name);
> > > >                     } while (--i >= 0);
> > > > +                   kfree_const(parent->name);
> > > > +                   kfree_const(parent->fw_name);
> > > 
> > > Both of them were just freed in the loop above, no?
> > for (i = 0, parent = parents; i < num_parents; i++, parent++)
> > Is 'parent' the same as the one from the loop above?
> 
> Yes. Did it change somehow?
parent++?
> 
> > 
> > Moreover, should 'parents[i].name' and 'parents[i].fw_name' be freed by
> > kfree_const()?
> > 
> 
> Yes? They're allocated with kstrdup_const() in clk_cpy_name(), or
> they're NULL by virtue of the kcalloc and then kfree_const() does
> nothing.
I re-examined clk_cpy_name(). They are the second parameter of 
clk_cpy_name(). The first parameter is allocated, not the second one.
So 'parent->name' and 'parent->fw_name' should be freed, not 
'parents[i].name' or 'parents[i].fw_name'. Am I totally misunderstanding
this clk_cpy_name()? :-(

Thanks
Gen
> 
> I'm having a hard time following what this patch is trying to fix. It
> looks unnecessary though so I'm going to drop it from the clk review
> queue.
> 

Re: [PATCH] clk: fix a missing-free bug in clk_cpy_name()

[Jiri Slaby]

On 07. 06. 19, 3:52, Gen Zhang wrote:
>>>>> @@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
>>>>>                             kfree_const(parents[i].name);
>>>>>                             kfree_const(parents[i].fw_name);
>>>>>                     } while (--i >= 0);
>>>>> +                   kfree_const(parent->name);
>>>>> +                   kfree_const(parent->fw_name);
>>>>
>>>> Both of them were just freed in the loop above, no?
>>> for (i = 0, parent = parents; i < num_parents; i++, parent++)
>>> Is 'parent' the same as the one from the loop above?
>>
>> Yes. Did it change somehow?
> parent++?

parent++ is done after the loop body. Or what do you mean?

>>> Moreover, should 'parents[i].name' and 'parents[i].fw_name' be freed by
>>> kfree_const()?
>>>
>>
>> Yes? They're allocated with kstrdup_const() in clk_cpy_name(), or
>> they're NULL by virtue of the kcalloc and then kfree_const() does
>> nothing.
> I re-examined clk_cpy_name(). They are the second parameter of 
> clk_cpy_name(). The first parameter is allocated, not the second one.
> So 'parent->name' and 'parent->fw_name' should be freed, not 
> 'parents[i].name' or 'parents[i].fw_name'. Am I totally misunderstanding
> this clk_cpy_name()? :-(

The second parameter (the source) is parent_data[i].*, not parents[i].*
(the destination). parent->fw_name and parent->name are properly freed
in the do {} while loop as parents[i].name and parents[i].fw_name, given
i hasn't changed yet. I am not sure what you mean at all. Are you
uncertain about the C code flow?

thanks,
-- 
js
suse labs

Re: [PATCH] clk: fix a missing-free bug in clk_cpy_name()

[Gen Zhang]

On Fri, Jun 07, 2019 at 11:10:37AM +0200, Jiri Slaby wrote:
> On 07. 06. 19, 3:52, Gen Zhang wrote:
> >>>>> @@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
> >>>>>                             kfree_const(parents[i].name);
> >>>>>                             kfree_const(parents[i].fw_name);
> >>>>>                     } while (--i >= 0);
> >>>>> +                   kfree_const(parent->name);
> >>>>> +                   kfree_const(parent->fw_name);
> >>>>
> >>>> Both of them were just freed in the loop above, no?
> >>> for (i = 0, parent = parents; i < num_parents; i++, parent++)
> >>> Is 'parent' the same as the one from the loop above?
> >>
> >> Yes. Did it change somehow?
> > parent++?
> 
> parent++ is done after the loop body. Or what do you mean?
> 
> >>> Moreover, should 'parents[i].name' and 'parents[i].fw_name' be freed by
> >>> kfree_const()?
> >>>
> >>
> >> Yes? They're allocated with kstrdup_const() in clk_cpy_name(), or
> >> they're NULL by virtue of the kcalloc and then kfree_const() does
> >> nothing.
> > I re-examined clk_cpy_name(). They are the second parameter of 
> > clk_cpy_name(). The first parameter is allocated, not the second one.
> > So 'parent->name' and 'parent->fw_name' should be freed, not 
> > 'parents[i].name' or 'parents[i].fw_name'. Am I totally misunderstanding
> > this clk_cpy_name()? :-(
> 
> The second parameter (the source) is parent_data[i].*, not parents[i].*
> (the destination). parent->fw_name and parent->name are properly freed
> in the do {} while loop as parents[i].name and parents[i].fw_name, given
> i hasn't changed yet. I am not sure what you mean at all. Are you
> uncertain about the C code flow?
> 
> thanks,
> -- 
> js
> suse labs
Thanks your patient explainaton. I think I need some time to figure out
this part of code.

Thanks
Gen

[PATCH] clk: fix a missing-free bug in clk_cpy_name()

[Gen Zhang]

In clk_cpy_name(), '*dst_p'('parent->name'and 'parent->fw_name') and 
'dst' are allcoted by kstrdup_const(). According to doc: "Strings 
allocated by kstrdup_const should be freed by kfree_const". So 
'parent->name', 'parent->fw_name' and 'dst' should be freed.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
---
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index aa51756..85c4d3f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3435,6 +3435,7 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
 	if (!dst)
 		return -ENOMEM;
 
+	kfree_const(dst);
 	return 0;
 }
 
@@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
 				kfree_const(parents[i].name);
 				kfree_const(parents[i].fw_name);
 			} while (--i >= 0);
+			kfree_const(parent->name);
+			kfree_const(parent->fw_name);
 			kfree(parents);
 
 			return ret;
---