drbd: fix NULL deref in remember_new_state
authorLars Ellenberg <lars.ellenberg@linbit.com>
Wed, 25 Feb 2015 12:53:28 +0000 (13:53 +0100)
committerJens Axboe <axboe@fb.com>
Wed, 25 Nov 2015 16:22:01 +0000 (09:22 -0700)
commit2b479766ee79a821f3cd7fad92fbcf2ff16cacb3
tree55b95aa5f7bcb8bc4066ee8704490d80bcfda093
parent84d34f2f0724f26de04f9863704a7ca797c0fd62
drbd: fix NULL deref in remember_new_state

The recent (not yet released) backport of the extended state broadcasts
to support the "events2" subcommand of drbdsetup had some glitches.

remember_old_state() would first count all connections with a
net_conf != NULL, then allocate a suitable array, then populate that
array with all connections found to have net_conf != NULL.

This races with the state change to C_STANDALONE,
and the NULL assignment there.

remember_new_state() then iterates over said connection array,
assuming that it would be fully populated.

But rcu_lock() just makes sure the thing some pointer points to,
if any, won't go away. It does not make the pointer itself immutable.

In fact there is no need to "filter" connections based on whether or not
they have a currently valid configuration.  Just record them always, if
they don't have a config, that's fine, there will be no change then.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
drivers/block/drbd/drbd_state.c