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drbd: fix an invalid memory access caused by incorrect use of list it…
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…erator

The bug is here:
	idr_remove(&connection->peer_devices, vnr);

If the previous for_each_connection() don't exit early (no goto hit
inside the loop), the iterator 'connection' after the loop will be a
bogus pointer to an invalid structure object containing the HEAD
(&resource->connections). As a result, the use of 'connection' above
will lead to a invalid memory access (including a possible invalid free
as idr_remove could call free_layer).

The original intention should have been to remove all peer_devices,
but the following lines have already done the work. So just remove
this line and the unneeded label, to fix this bug.

Cc: stable@vger.kernel.org
Fixes: c06ece6 ("drbd: Turn connection->volumes into connection->peer_devices")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Xiaomeng Tong authored and Jens Axboe committed Apr 6, 2022
1 parent aadb22b commit ae4d37b
Showing 1 changed file with 2 additions and 4 deletions.
6 changes: 2 additions & 4 deletions drivers/block/drbd/drbd_main.c
Original file line number Diff line number Diff line change
Expand Up @@ -2773,12 +2773,12 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig

if (init_submitter(device)) {
err = ERR_NOMEM;
goto out_idr_remove_vol;
goto out_idr_remove_from_resource;
}

err = add_disk(disk);
if (err)
goto out_idr_remove_vol;
goto out_idr_remove_from_resource;

/* inherit the connection state */
device->state.conn = first_connection(resource)->cstate;
Expand All @@ -2792,8 +2792,6 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
drbd_debugfs_device_add(device);
return NO_ERROR;

out_idr_remove_vol:
idr_remove(&connection->peer_devices, vnr);
out_idr_remove_from_resource:
for_each_connection(connection, resource) {
peer_device = idr_remove(&connection->peer_devices, vnr);
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