`On Wed, 2018-10-24 at 18:32 +0200, Willy Tarreau wrote:> On Wed, Oct 24, 2018 at 09:23:19AM -0700, Joe Perches wrote:> > On Wed, 2018-10-24 at 17:57 +0200, Willy Tarreau wrote:> > > On Wed, Oct 24, 2018 at 11:47:29PM +0800, Wang Hai wrote:> > > > To determine whether len is less than zero, it should be put before > > > > the function min_t, because the return value of min_t is not likely > > > > to be less than zero.> > > > > > Huh? First, the <0 test is made on "len", not "min_t", so it still> > > is signed. Second, you're in fact completely removing the test here,> > > look :> > > > > > >  	struct net *net = sock_net(sk);> > > >  	int val, len;> > > > > > > > +	len = min_t(unsigned int, len, sizeof(int));> > > > +> > > > > > len is used uninitialized here, so the result is undefined.> > > > > > >  	if (get_user(len, optlen))> > > >  		return -EFAULT;> > > > > > Then it gets overridden by get_user()> > > > > > > -	len = min_t(unsigned int, len, sizeof(int));> > > > -> > > > > > Then its positive values are not bounded anymore since you moved the test.> > > > Not quite.> > > > Problem here is negative values are tested as> > large positive values and limited to 4> > > > ie:> > 	ien len = -1,> > 	len = min_t(unsigned int, len, sizeof(int));> > > > len is now 4> > > > > >  	if (len < 0)> > > >  		return -EINVAL;> > > > So this test len < 0 could be moved up above min_t> > It could indeed, or we could also have min_t() done on an int instead> of an unsigned int and this would avoid the need to shuffle the code> around and open a huge hole like this one.I think if the point is to test for negative numbers,it's clearer to do that before using min_t.and it'sprobably clearer not to use min_t at all.	if (get_user(len, optlen))		return -EFAULT;	if (len < 0)		return -EINVAL;	if (len > sizeof(int))		len = sizeof(int);`