[Cocci] [PATCHv1 1/3] coccinelle: also catch kzfree() issues

[ydroneaud@opteya.com (Yann Droneaud)]

Le lundi 22 f?vrier 2016 ? 09:20 -0500, Julia Lawall a ?crit?:
> On Mon, 22 Feb 2016, Yann Droneaud wrote:
> 
> > Since commit 3ef0e5ba4673 ('slab: introduce kzfree()'),
> > kfree() is no more the only function to be considered.
> >
> > In particular, kzfree() must not be called on memory
> > allocated through devm_*() functions.
> >
> > Cc: Johannes Weiner <hannes@cmpxchg.org>
> > Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
> > ---
> > Hi Julia,
> >
> > As you suggested, I've use disjunctions instead of regular
> > expressions (which I managed to use incorrectly: eg.
> > without ^...$ they catch other functions than kfree(),
> > such as kfree_skb()).
> >
> > I've think we should also catch krealloc(, size), where size
> > is 0, but it's beyond my understanding of coccinelle if size
> > is not a plain 0 constant.
> >
> > Perhaps you could help me for this one.
> 
> Do you have some examples?

I don't have any real world examples (hopefully) and I don't think it's
going to catch issues, as it's unlikely someone would write
krealloc(ptr, 0) instead of kfree().

> ? Coccinelle is not very good at tracking
> values.? You can say something like:
> 
> size = 0
> ... when != size = e
> krealloc(...,size)
> 

It works for the most simple cases I can think of. Thanks a lot !

> I don't know if that would be useful in practice though.
> 

It will be difficult to shoehorn such construct in the dijunctions
added here.

Perhaps we could add a new cocci rules file that would translate such
call to krealloc() to kfree():

@@
expression e;
expression p;
identifier size;
@@
? size = 0
? ... when != size = e
-??krealloc(p,size)
+??kfree(p)


@@
expression p;
@@
-??krealloc(p, 0)
+??kfree(p)

But I'm not sure it worth it.

> > Regards.
> >
> >? scripts/coccinelle/free/devm_free.cocci |? 2 ++
> >? scripts/coccinelle/free/kfree.cocci???? | 18 +++++++++++++++---
> >? scripts/coccinelle/free/kfreeaddr.cocci |? 6 +++++-
> >? 3 files changed, 22 insertions(+), 4 deletions(-)
> >
> > diff --git a/scripts/coccinelle/free/devm_free.cocci
> b/scripts/coccinelle/free/devm_free.cocci
> > index 3d9349012bb3..83c03adec1c5 100644
> > --- a/scripts/coccinelle/free/devm_free.cocci
> > +++ b/scripts/coccinelle/free/devm_free.cocci
> > @@ -48,6 +48,8 @@ position p;
> >? (
> >? * kfree at p(x)
> >? |
> > +* kzfree at p(x)
> > +|
> >? * free_irq at p(x)
> >? |
> >? * iounmap at p(x)
> > diff --git a/scripts/coccinelle/free/kfree.cocci
> b/scripts/coccinelle/free/kfree.cocci
> > index 577b78056990..ac438da4fd7b 100644
> > --- a/scripts/coccinelle/free/kfree.cocci
> > +++ b/scripts/coccinelle/free/kfree.cocci
> > @@ -20,7 +20,11 @@ expression E;
> >? position p1;
> >? @@
> >
> > -kfree at p1(E)
> > +(
> > +* kfree at p1(E)
> > +|
> > +* kzfree at p1(E)
> > +)
> >
> >? @print expression@
> >? constant char [] c;
> > @@ -60,7 +64,11 @@ position ok;
> >? @@
> >
> >? while (1) { ...
> > -? kfree at ok(E)
> > +(
> > +* kfree at ok(E)
> > +|
> > +* kzfree at ok(E)
> > +)
> >??? ... when != break;
> >??????? when != goto l;
> >??????? when forall
> > @@ -74,7 +82,11 @@ statement S;
> >? position free.p1!=loop.ok,p2!={print.p,sz.p};
> >? @@
> >
> > -kfree at p1(E,...)
> > +(
> > +* kfree at p1(E,...)
> > +|
> > +* kzfree at p1(E,...)
> > +)
> >? ...
> >? (
> >?? iter(...,subE,...) S // no use
> > diff --git a/scripts/coccinelle/free/kfreeaddr.cocci
> b/scripts/coccinelle/free/kfreeaddr.cocci
> > index ce8aacc314cb..d46063b1db8b 100644
> > --- a/scripts/coccinelle/free/kfreeaddr.cocci
> > +++ b/scripts/coccinelle/free/kfreeaddr.cocci
> > @@ -16,7 +16,11 @@ identifier f;
> >? position p;
> >? @@
> >
> > +(
> >? * kfree at p(&e->f)
> > +|
> > +* kzfree at p(&e->f)
> > +)
> >
> >? @script:python depends on org@
> >? p << r.p;
> > @@ -28,5 +32,5 @@ cocci.print_main("kfree",p)
> >? p << r.p;
> >? @@
> >
> > -msg = "ERROR: kfree of structure field"
> > +msg = "ERROR: invalid free of structure field"
> >? coccilib.report.print_report(p[0],msg)
> > --
> > 2.5.0
> >
> >

Regards.

--?
Yann Droneaud
OPTEYA