Author: markj
Date: Sat Nov 24 16:41:29 2018
New Revision: 340897
URL: https://svnweb.freebsd.org/changeset/base/340897

Log:
  Lock the knlist before releasing the in-flux state in knote_fork().
  
  Otherwise there is a window, before iteration is resumed, during which
  the knote may be freed.  The in-flux state ensures that the knote will
  not be removed from the knlist while locks are dropped.
  
  PR:           228858
  Reviewed by:  kib
  Tested by:    pho
  MFC after:    3 days
  Sponsored by: The FreeBSD Foundation
  Differential Revision:        https://reviews.freebsd.org/D18316

Modified:
  head/sys/kern/kern_event.c

Modified: head/sys/kern/kern_event.c
==============================================================================
--- head/sys/kern/kern_event.c  Sat Nov 24 16:31:43 2018        (r340896)
+++ head/sys/kern/kern_event.c  Sat Nov 24 16:41:29 2018        (r340897)
@@ -600,10 +600,10 @@ knote_fork(struct knlist *list, int pid)
                        kn->kn_fflags |= NOTE_TRACKERR;
                if (kn->kn_fop->f_event(kn, NOTE_FORK))
                        KNOTE_ACTIVATE(kn, 0);
+               list->kl_lock(list->kl_lockarg);
                KQ_LOCK(kq);
                kn_leave_flux(kn);
                KQ_UNLOCK_FLUX(kq);
-               list->kl_lock(list->kl_lockarg);
        }
        list->kl_unlock(list->kl_lockarg);
 }
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