linux-kernel - Re: [PATCH] Avoid potential NULL deref in scripts/genksyms/lex.l

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Date:	Mon, 25 Jun 2007 01:08:27 +0200
From:	"Jesper Juhl" <jesper.juhl@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	"Richard Henderson" <rth@...u.edu>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Avoid potential NULL deref in scripts/genksyms/lex.l

On 25/06/07, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Mon, 25 Jun 2007 00:02:03 +0200 "Jesper Juhl" <jesper.juhl@...il.com> wrote:
>
> > > > +      if (!file || !e)
> > > > +     exit(1);
> > > >        *e = '\0';
> > > >        cur_filename = memcpy(xmalloc(e-file+1), file, e-file+1);
> > > >        cur_line = atoi(yytext+2);
> > >
> > > I don't think the bug which you're fixing can occur:
> > >
> > > ^#[ \t]+{INT}[ \t]+\"[^\"\n]+\".*\n     return FILENAME;
> > >
> > > has anyone reported crashes in there?
> > >
> >
> > It may indeed not be possible. Found by inspection, not by any actual
> > observed crashes.
> > But does it really hurt to be defensive here? In case it can somehow
> > be caused to fail, with my patch it'll fail a bit nicer :) It's not
> > like it's at all speed critical code that will be hurt by that extra
> > 'if'...
>
> We can only get NULL pointers here if the regexp is wrong or if there's
> a bug in the regexp parser.  Getting a coredump at the failure site is
> much better behaviour than mysteriously exiting.
>
Fair enough. Just ignore the patch then :-)

-- 
Jesper Juhl <jesper.juhl@...il.com>
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