[lxc-devel] memory leak

[Serge Hallyn]

Quoting Dwight Engen (dwight.engen at oracle.com):
> Hi guys,
> 
> So the line:
> 
>   r = lxc_grow_array((void ***)&h->all_mount_points,
>                      &h->all_mount_point_capacity, k + 1, 4);
> 
> in cgroup.c shows up in valgrind as a leak. I thought the appropriate
> fix was:
> 
> diff --git a/src/lxc/cgroup.c b/src/lxc/cgroup.c
> index e27bc03..c5dc7e2 100644
> --- a/src/lxc/cgroup.c
> +++ b/src/lxc/cgroup.c
> @@ -1563,6 +1563,7 @@ void lxc_cgroup_hierarchy_free(struct
> cgroup_hierarchy *h) if (!h)
>  		return;
>  	lxc_free_array((void **)h->subsystems, free);
> +	lxc_free_array((void **)h->all_mount_points, free);
>  	free(h);
>  }
>  
> which does free the allocated memory, but then causes a segv the next
> time free(line) in find_hierarchy_mountpts() is called. The trap is in
> libc::malloc_consolidate() so I think there is heap corruption going
> on. Any ideas?

Well the exact symptoms you describe are a bit fishy - I'd
expect a double-free warning right at the line you added.

I think you want to just free(h->all_mount_points).  The
all_mount_points[i] entries get set to 'mount_point' which are
also pointed to by meta_data, and which you freed right before
the loop calling lxc_cgroup_hierarchy_free().

Does just using free at this same spot fix it for you?

-serge