Re: [PATCH] Change judgment len position
From: Willy Tarreau
Date: Wed Oct 24 2018 - 11:58:11 EST
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,
> 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.
> if (len < 0)
> return -EINVAL;
Then only negative values are dropped. So unless I'm missing something
obvious, you're just allowing len to be as large as 2GB-1 based on the
user's fed optlen.
Am I wrong ?