[parted-devel] BUG: ped_exception_throw() can go to endless loop allocating memory

[Petr Uzel]

On Wed, Nov 26, 2008 at 05:22:05AM -0500, Joel Granados wrote:
> Can you please send a `git diff`?

I actually do not have one - since I'am not sure about the patch I
wanted to discuss what/how has to be changed :)

> 
> Regards
> ----- "Petr Uzel" <petr.uzel at suse.cz> wrote:
> 
> > Hi list!
> > 
> > 1	PedExceptionOption
> > 2	ped_exception_throw (PedExceptionType ex_type,
> > 3			     PedExceptionOption ex_opts, const char* message, ...)
> > 4	{
> > 5		va_list		arg_list;
> > 6		int result;
> > 7		static int size = 1000;
> > 
> > 8		if (ex)
> > 9			ped_exception_catch ();
> > 
> > 10		ex = (PedException*) malloc (sizeof (PedException));
> > 11		if (!ex)
> > 12			goto no_memory;
> > 
> > 13		ex->type = ex_type;
> > 14		ex->options = ex_opts;
> > 
> > 15		while (message) {
> > 16				ex->message = (char*) malloc (size * sizeof (char));
> > 17				if (!ex->message)
> > 18						goto no_memory;
> > 
> > 19				va_start (arg_list, message);
> > 20				result = vsnprintf (ex->message, size, message, arg_list);
> > 21				va_end (arg_list);
> > 
> > 22				if (result > -1 && result < size)
> > 23						break;
> > 
> > 24				size += 10;
> > 25				free (ex->message);
> > 26		}
> > 
> > 27		return do_throw ();
> > 
> > If this function gets NULL in 'message' parameter, it will go into
> > endless loop allocating memory because vsnprintf() on line 20 will
> > keep returning -1 and thus the condition on line 22 will never be
> > true.
> > 
> > There is at least one place where ped_exception_throw() is called
> > with
> > NULL : libparted/labels/dasd.c:243    [*]
> > 
> > I suggest to:
> > a) PED_ASSERT(message != NULL) somewhere in ped_exception_throw()
> > b) change the condition on line 22 to be just 'if (result < size)',
> > because when vsnprintf() once returned -1, it will probably keep
> > returning the same even with larger buffer.
> > c) fix [*] to something more appropriate, such as:
> > 
> > ped_exception_throw(PED_EXCEPTION_ERROR, PED_EXCEPTION_OK,
> >                    _("%s is corrupted"),
> >                    dev->path);
> > 
> > Of course the 'is corrupted' text has to be changed to something
> > better.
> > 
> > BTW isn't the while loop a typical case where realloc() would be more
> > appropriate then malloc()/free() ?
> > 
> > 
> > What do you guys think?
> > 
> > 
> > -- 
> > Best regards / s pozdravem
> > 
> > Petr Uzel, Packages maintainer
> > ---------------------------------------------------------------------
> > SUSE LINUX, s.r.o.                          e-mail: puzel at suse.cz
> > Lihovarská 1060/12                          tel: +420 284 028 964
> > 190 00 Prague 9                             fax: +420 284 028 951
> > Czech Republic                              http://www.suse.cz
> > 
> > _______________________________________________
> > parted-devel mailing list
> > parted-devel at lists.alioth.debian.org
> > http://lists.alioth.debian.org/mailman/listinfo/parted-devel
> 
> -- 
> Joel Andres Granados
> Red Hat / Brno Czech Republic

-- 
Best regards / s pozdravem

Petr Uzel, Packages maintainer
---------------------------------------------------------------------
SUSE LINUX, s.r.o.                          e-mail: puzel at suse.cz
Lihovarská 1060/12                          tel: +420 284 028 964
190 00 Prague 9                             fax: +420 284 028 951
Czech Republic                              http://www.suse.cz