Author :
mvs
Date :
2020-10-03 00:23:55
Hash :997bae9a Message :Introduce `if_cloners_lock' rwlock and use it to serialize
if_clone_{create,destroy}(). This fixes the races described below.
if_clone_{create,destroy}() are kernel locked, but since they touch
various sleep points introduced by rwlocks and M_WAITOK allocations,
without serialization they can intersect due to race condition.
The avoided races are:
1. While performing if_clone_create(), concurrent thread which performing
if_clone_create() can attach `ifp' with the same `if_xname' and made
inconsistent `if_list' where all attached interfaces linked.
2. While performing if_clone_create(), concurrent thread which performing
if_clone_destroy() can kill this incomplete `ifp'.
3. While performing if_clone_destroy(), concurrent thread which performing
if_clone_destroy() can kill this dying `ifp'.
ok claudio@ kn@ mpi@ sashan@
mvs