Re: [PATCH 3/3] socket: prevent recvfrom from returning garbage

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Fri, Aug 24, 2018 at 04:44:41PM +0300, Alexander Turenko wrote:
> On Fri, Aug 24, 2018 at 04:07:48PM +0300, Vladimir Davydov wrote:
> > On Fri, Aug 24, 2018 at 05:47:39AM +0300, Alexander Turenko wrote:
> > > In C recvfrom function sets addrlen parameter to zero when called on TCP
> > > socket (at least on Linux). The src_addr parameter can contain garbage
> > > in the case, so we should not dereference it.
> > > 
> > > Before this commit socket:recvfrom() can return 'from' table with only
> > > family field (don't sure why, but addr->sa_family often contain PF_INET
> > > value in my case) or return nil depending on the garbage at the address.
> > > Now it always return nil.
> > > ---
> > >  src/lua/socket.c | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > 
> > Could you please add a test case?
> 
> Added in the previous commit ('case: recvfrom truncate the message with
> tcp'). The main purpose of the test case is another, but when added I
> found the flakiness ('from' could be {family = 'AF_INET'} or nil from
> time to time) and fixed it here.
> 
> How to better handle this? I suppose I should add a comment to the test
> case that it also test this case?

This patch is pretty straightforward and raises no questions, in
contrast to patches 1 and 2. If you equipped it with a test and
rebased on top of 1.10 (or should it be 1.9?), I'd pushed it right
away.