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

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Message-Id: <20070624160014.84e26d35.akpm@linux-foundation.org>
Date:	Sun, 24 Jun 2007 16:00:14 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Jesper Juhl" <jesper.juhl@...il.com>
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 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.
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