Re: [PATCH net] nfc: avoid potential race condition

Jakub Kicinski
2021-09-24T20:14:44Z

On Fri, 24 Sep 2021 10:21:33 +0200 Krzysztof Kozlowski wrote:
> On 23/09/2021 14:22, Dan Carpenter wrote:
> > On Thu, Sep 23, 2021 at 09:26:51AM +0200, Krzysztof Kozlowski wrote:
> >> On 23/09/2021 08:50, Dan Carpenter wrote:
> [...]
> >>
> >> I think the difference between this llcp_sock code and above transport,
> >> is lack of writer to llcp_sock->local with whom you could race.
> >>
> >> Commits c0cfa2d8a788fcf4 and 6a2c0962105ae8ce causing the
> >> multi-transport race show nicely assigns to vsk->transport when module
> >> is unloaded.
> >>
> >> Here however there is no writer to llcp_sock->local, except bind and
> >> connect and their error paths. The readers which you modify here, have
> >> to happen after bind/connect. You cannot have getsockopt() or release()
> >> before bind/connect, can you? Unless you mean here the bind error path,
> >> where someone calls getsockopt() in the middle of bind()? Is it even
> >> possible?
> >>
> >
> > I don't know if this is a real issue either.
> >
> > Racing with bind would be harmless. The local pointer would be NULL and
> > it would return harmlessly. You would have to race with release and
> > have a third trying to release local devices. (Again that might be
> > wild imagination. It may not be possible).
>
> Indeed. The code looks reasonable, though, so even if race is not really
> reproducible:
>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

Would you mind making a call if this is net (which will mean stable) or
net-next material (without the Fixes tags) and reposting? Thanks! :)