Re: [PATCH net v2] ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF

[Sebastian Andrzej Siewior]

On 2026-07-07 09:39:01 [-0700], Paul E. McKenney wrote:
> Alternatives include:
> 
> o	Provide a patch like that above, but only execute the
> 	rcu_barrier() in some debug mode.  If your code works when
> 	that debug is enabled but does not otherwise, you add the
> 	rcu_barrier().
> 
> o	If debug is enabled, make rcu_do_batch() check the function
> 	before invoking it.  If the function is not mapped, issue a
> 	diagnostic, and don't try to invoke the function.  (But is
> 	there a sufficiently cheap way to check for the function not
> 	being mapped?)

In both cases you would see a backtrace and the name of the last
unloaded module. And since we don't see a lot of these reports, people
either don't run into this because it does not exist or RCU is quick
enough.

> 
> 							Thanx, Paul

Sebastian