Re: [PATCH v4] netlink: Fix autobind race condition that leads to zero port ID

[David Miller]

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Fri, 18 Sep 2015 19:16:50 +0800

> The commit c0bb07df7d981e4091432754e30c9c720e2c0c78 ("netlink:
> Reset portid after netlink_insert failure") introduced a race
> condition where if two threads try to autobind the same socket
> one of them may end up with a zero port ID.  This led to kernel
> deadlocks that were observed by multiple people.
> 
> This patch reverts that commit and instead fixes it by introducing
> a separte rhash_portid variable so that the real portid is only set
> after the socket has been successfully hashed.
> 
> Fixes: c0bb07df7d98 ("netlink: Reset portid after netlink_insert failure")
> Reported-by: Tejun Heo <tj@xxxxxxxxxx>
> Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

Applied and queued up for -stable, thanks Herbert.
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