Re: [PATCH 1/2] scripts/coccinelle: catch freeing cryptographic structures via kfree

[Konstantin Khlebnikov]

On 2014-11-17 18:30, Julia Lawall wrote:
> On Mon, 17 Nov 2014, Konstantin Khlebnikov wrote:
>
> > Structures allocated by crypto_alloc_* must be freed using crypto_free_*.
> >
> > Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@xxxxxxxxxxx>
> > ---
> >   scripts/coccinelle/free/crypto_free.cocci |   45 +++++++++++++++++++++++++++++
> >   1 file changed, 45 insertions(+)
> >   create mode 100644 scripts/coccinelle/free/crypto_free.cocci
> >
> > diff --git a/scripts/coccinelle/free/crypto_free.cocci b/scripts/coccinelle/free/crypto_free.cocci
> > new file mode 100644
> > index 0000000..0799b70
> > --- /dev/null
> > +++ b/scripts/coccinelle/free/crypto_free.cocci
> > @@ -0,0 +1,45 @@
> > +///
> > +/// Structures allocated by crypto_alloc_* must be freed using crypto_free_*.
> > +/// This finds freeing them by kfree.
> > +///
> > +// Confidence: Moderate
> > +// Copyright: (C) 2014 Konstantin Khlebnikov,  GPLv2.
> > +// Comments: There are false positives in crypto/ where they are actually freed.
> > +// Keywords: crypto, kfree
> > +// Options: --no-includes --include-headers
> > +
> > +virtual org
> > +virtual report
> > +virtual context
> > +
> > +@r depends on context || org || report@
> > +expression x;
> > +identifier crypto_alloc =~ "^crypto_alloc_";
> > +@@
> > +
> > +(
> > + x = crypto_alloc(...)
> > +)
> You can drop the outer parentheses, in this case and in the kfree case.
>
> Are there many of these crypto_alloc_ functions?  It would be nicer to
> avoid the regular expression.  For one thing, you don't have much control
> over what it matches, and for another thing Coccinelle will not be able to
> optimize the selection of files.  With the regular expression it will have
> to parse every file and analyze every function, which will be slow.

As I see here is eight .. ten candidates, maybe some of them are internal.
Ok, I'll resend patch without regex.

> julia
>
> > +
> > +@pb@
> > +expression r.x;
> > +position p;
> > +@@
> > +
> > +(
> > +* kfree@p(x)
> > +)
> > +
> > +@script:python depends on org@
> > +p << pb.p;
> > +@@
> > +
> > +msg="WARNING: invalid free of crypto_alloc_* allocated data"
> > +coccilib.org.print_todo(p[0], msg)
> > +
> > +@script:python depends on report@
> > +p << pb.p;
> > +@@
> > +
> > +msg="WARNING: invalid free of crypto_alloc_* allocated data"
> > +coccilib.report.print_report(p[0], msg)

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