Re: [PATCH 1/1] ipv4: ipmr_expire_timer causes crash when removing net namespace

On Mon, Aug 20, 2012 at 10:29 PM, Eric Dumazet [off-list ref] wrote:

On Mon, 2012-08-20 at 17:15 -0700, Francesco Ruggeri wrote:

quoted

I
+static void ipmr_free_table(struct mr_table *mrt)
+{
+     del_timer(&mrt->ipmr_expire_timer);
+     mroute_clean_tables(mrt);
+     kfree(mrt);
+}

Seems racy to me.

del_timer() doesnt make sure timer is completely disabled.

Probably need spin_lock_bh(&mfc_unres_lock) /
spin_unlock_bh(&mfc_unres_lock), and maybe del_timer_sync()

I see your point, del_timer_sync should be used to take care of any
pending timers.
I am not sure about the need for further locking though. This function
simply replaces a direct call to kfree(mrt), so I assume by this point
today's code already makes sure no one is going to access this
structure (including to start the timer), or we have a bigger problem
than just the timer.
Maybe someone familiar with ipmr can comment.

Francesco