Messages in this thread | | | Subject | Re: [PATCH] Change judgment len position | From | Joe Perches <> | Date | Wed, 24 Oct 2018 09:23:19 -0700 |
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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
> 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 ? > > Willychee
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