Hello,
On Sun, Sep 27, 2015 at 04:10:41AM +0800, Herbert Xu wrote:
> Well guess what the bug that you have discovered supposedly due to
> a missing barrier in netlink_connect has nothing to do with the
> barrier. Instead it is caused by a logical error elsewhere that
> would have gone unnoticed o
On Sat, Sep 26, 2015 at 04:05:18PM -0400, Tejun Heo wrote:
>
> Frankly, I don't understand what you've been trying to achieve.
> You're actively disregarding best practices (like terminating
> synchronization where it starts) and reach the target state by doing a
> browian motion in the solution s
Hello,
On Sun, Sep 27, 2015 at 03:55:48AM +0800, Herbert Xu wrote:
> Well I disagree. When I say that it returns to user-space I really
> mean that the next time we use portid via the same call path that
> triggered the connect we must be checking nlk->bound anyway.
>
> Good luck finding more bu
On Sat, Sep 26, 2015 at 03:52:45PM -0400, Tejun Heo wrote:
>
> Ah, yeah, you're right. We need to check that there because it may
> contain a garbage value. I still think it'd better to use
> netlink_bound() test in connect() too tho.
Well I disagree. When I say that it returns to user-space I
Hello,
On Sun, Sep 27, 2015 at 03:49:16AM +0800, Herbert Xu wrote:
> If the autobind is not complete then netlink_getname must return
> zero rather than some garbage portid that belongs to somebody
> else's socket. That's what we did before any of this lockless
> code was introduced.
>
> If you
On Sat, Sep 26, 2015 at 03:45:54PM -0400, Tejun Heo wrote:
> Hello, Herbert.
>
> On Sun, Sep 27, 2015 at 03:41:10AM +0800, Herbert Xu wrote:
> > Thread 1Thread 2
> > sendmsg getsockname
> > netlink_autobindnetlink_getname
> >
> >
Hello, Herbert.
On Sun, Sep 27, 2015 at 03:41:10AM +0800, Herbert Xu wrote:
> Thread 1 Thread 2
> sendmsg getsockname
> netlink_autobindnetlink_getname
>
> Thread 2 should not have to do anything special to guarantee that
>
On Sat, Sep 26, 2015 at 02:09:03PM -0400, Tejun Heo wrote:
>
> > @@ -1628,7 +1632,7 @@ static int netlink_getname(struct socket *sock,
> > struct sockaddr *addr,
> > nladdr->nl_pid = nlk->dst_portid;
> > nladdr->nl_groups = netlink_group_mask(nlk->dst_group);
> > } else
Hello, Herbert.
On Sat, Sep 26, 2015 at 09:16:21PM +0800, Herbert Xu wrote:
> You misunderstood what I wrote. I was not basing this on whether
> user-space transitions contained a barrier, but on the fact that
> the next syscall must recheck nlk->bound before using nlk->portid.
But that isn't wh
On Fri, Sep 25, 2015 at 11:01:13AM -0400, Tejun Heo wrote:
>
> I'm not even sure we guarantee memory barrier on kernel/user
> crossings. In practice, we probably have enough barriers (e.g. some
> syscall traps imply barrier) but I can't think of a reason why we'd
> guarantee the existence of barr
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