Re: [RFC][PATCH 1/9] klp: Fix obvious RCU fail

[Peter Zijlstra]

On Sun, Mar 01, 2015 at 09:09:24PM +0100, Jiri Kosina wrote:
> On Sat, 28 Feb 2015, Peter Zijlstra wrote:
> 
> > While one must hold RCU-sched (aka. preempt_disable) for find_symbol()
> > one must equally hold it over the use of the object returned.
> > 
> > The moment you release the RCU-sched read lock, the object can be dead
> > and gone.
> > 
> > Cc: Seth Jennings <sjenning@xxxxxxxxxx>
> > Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> > Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> > Cc: Miroslav Benes <mbenes@xxxxxxx>
> > Cc: Petr Mladek <pmladek@xxxxxxx>
> > Cc: Jiri Kosina <jkosina@xxxxxxx>
> > Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> > Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> 
> Acked-by: Jiri Kosina <jkosina@xxxxxxx>
> 
> I guess you'll be taking this together with the series, so I am not 
> applying it.

Feel free to take it; this series might take a wee while longer to
mature.

That said; I do have a follow up question on that code. So now you've
successfully obtained an address in module space; but the moment you
release that RCU-sched lock, the module can be gone.

How does the whole live patching stuff deal with module removal during
patching?
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