Re: [PATCH v2] netlink: Replace rhash_portid with bound

[David Miller]

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 22 Sep 2015 11:38:56 +0800

> The commit 1f770c0a09da855a2b51af6d19de97fb955eca85 ("netlink:
> Fix autobind race condition that leads to zero port ID") created
> some new races that can occur due to inconcsistencies between the
> two port IDs.
> 
> Tejun is right that a barrier is unavoidable.  Therefore I am
> reverting to the original patch that used a boolean to indicate
> that a user netlink socket has been bound.
> 
> Barriers have been added where necessary to ensure that a valid
> portid and the hashed socket is visible.
> 
> I have also changed netlink_insert to only return EBUSY if the
> socket is bound to a portid different to the requested one.  This
> combined with only reading nlk->bound once in netlink_bind fixes
> a race where two threads that bind the socket at the same time
> with different port IDs may both succeed.
> 
> Fixes: 1f770c0a09da ("netlink: Fix autobind race condition that leads to zero port ID")
> Reported-by: Tejun Heo <tj@xxxxxxxxxx>
> Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

I've decided to apply this and queue it up for -stable.

Thanks everyone.
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