The code was set up so that it would free the individual items and the data
in `freeListData`, but there was already a Go `defer` to free the data item,
resulting in a double free.
Remove the `free` in `freeListData` and leave the original one.
In addition, move the `defer` for freeing the list data before the error
check, so that the data is also free in the error case. This just removes
a minor leak.
This vulnerability was discovered by:
Jasiel Spelman of Trend Micro Zero Day Initiative and Trend Micro Team Nebula
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Justin Cormack