Re: [PATCH v2] netlink: do not set cb_running if dump's start() errs

[David Miller]

From: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
Date: Mon,  9 Oct 2017 14:14:51 +0200

> It turns out that multiple places can call netlink_dump(), which means
> it's still possible to dereference partially initialized values in
> dump() that were the result of a faulty returned start().
> 
> This fixes the issue by calling start() _before_ setting cb_running to
> true, so that there's no chance at all of hitting the dump() function
> through any indirect paths.
> 
> It also moves the call to start() to be when the mutex is held. This has
> the nice side effect of serializing invocations to start(), which is
> likely desirable anyway. It also prevents any possible other races that
> might come out of this logic.
> 
> In testing this with several different pieces of tricky code to trigger
> these issues, this commit fixes all avenues that I'm aware of.
> 
> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>

Applied and queued up for -stable.