drbd: prevent NULL pointer deref when resuming diskless primary (9fa48269) · Commits · 戴 / test

In a multiple error scenario, we may end up with a "frozen" Primary, that has no access to any data (no local disk, no replication link). If we then resume-io, we try to generate a new data generation id, which will fail if there is no longer a local disk. Double check for available local data, which prevents the NULL pointer deref. If we are diskless, turn the resume-io in this situation into the first stage of a "force down", by bumping the "effective" data gen id, which will prevent later attach or connect to the former data set without first being demoted (deconfigured). 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_nl.c

+24 −1

Original line number	Diff line number	Diff line
		@@ -2920,7 +2920,30 @@ int drbd_adm_resume_io(struct sk_buff skb, struct genl_info info)
		mutex_lock(&adm_ctx.resource->adm_mutex);
		device = adm_ctx.device;
		if (test_bit(NEW_CUR_UUID, &device->flags)) {
		if (get_ldev_if_state(device, D_ATTACHING)) {
		drbd_uuid_new_current(device);
		put_ldev(device);
		} else {
		/* This is effectively a multi-stage "forced down".
		* The NEW_CUR_UUID bit is supposedly only set, if we
		* lost the replication connection, and are configured
		* to freeze IO and wait for some fence-peer handler.
		* So we still don't have a replication connection.
		* And now we don't have a local disk either. After
		* resume, we will fail all pending and new IO, because
		* we don't have any data anymore. Which means we will
		* eventually be able to terminate all users of this
		* device, and then take it down. By bumping the
		* "effective" data uuid, we make sure that you really
		* need to tear down before you reconfigure, we will
		* the refuse to re-connect or re-attach (because no
		* matching real data uuid exists).
		*/
		u64 val;
		get_random_bytes(&val, sizeof(u64));
		drbd_set_ed_uuid(device, val);
		drbd_warn(device, "Resumed without access to data; please tear down before attempting to re-configure.\n");
		}
		clear_bit(NEW_CUR_UUID, &device->flags);
		}
		drbd_suspend_io(device);

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