Re: [net-next V6 PATCH 1/5] bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP

Daniel Borkmann
2017-10-10T22:48:46Z

On 10/10/2017 02:47 PM, Jesper Dangaard Brouer wrote:
[...]
> +static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
> +{
> + struct bpf_cpu_map *cmap;
> + int err = -ENOMEM;
> + u64 cost;
> + int ret;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return ERR_PTR(-EPERM);
> +
> + /* check sanity of attributes */
> + if (attr->max_entries == 0 || attr->key_size != 4 ||
> + attr->value_size != 4 || attr->map_flags & ~BPF_F_NUMA_NODE)
> + return ERR_PTR(-EINVAL);
> +
> + cmap = kzalloc(sizeof(*cmap), GFP_USER);
> + if (!cmap)
> + return ERR_PTR(-ENOMEM);
> +
> + /* mandatory map attributes */
> + cmap->map.map_type = attr->map_type;
> + cmap->map.key_size = attr->key_size;
> + cmap->map.value_size = attr->value_size;
> + cmap->map.max_entries = attr->max_entries;
> + cmap->map.map_flags = attr->map_flags;
> + cmap->map.numa_node = bpf_map_attr_numa_node(attr);
> +
> + /* Pre-limit array size based on NR_CPUS, not final CPU check */
> + if (cmap->map.max_entries > NR_CPUS)
> + return ERR_PTR(-E2BIG);

We still have a leak here, meaning kfree(cmap) is missing on above error.

> +
> + /* make sure page count doesn't overflow */
> + cost = (u64) cmap->map.max_entries * sizeof(struct bpf_cpu_map_entry *);
> + cost += cpu_map_bitmap_size(attr) * num_possible_cpus();
> + if (cost >= U32_MAX - PAGE_SIZE)
> + goto free_cmap;
> + cmap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
> +
> + /* Notice returns -EPERM on if map size is larger than memlock limit */
> + ret = bpf_map_precharge_memlock(cmap->map.pages);
> + if (ret) {
> + err = ret;
> + goto free_cmap;
> + }
> +
> + /* A per cpu bitfield with a bit per possible CPU in map */
> + cmap->flush_needed = __alloc_percpu(cpu_map_bitmap_size(attr),
> + __alignof__(unsigned long));
> + if (!cmap->flush_needed)
> + goto free_cmap;
> +
> + /* Alloc array for possible remote "destination" CPUs */
> + cmap->cpu_map = bpf_map_area_alloc(cmap->map.max_entries *
> + sizeof(struct bpf_cpu_map_entry *),
> + cmap->map.numa_node);
> + if (!cmap->cpu_map)
> + goto free_cmap;
> +
> + return &cmap->map;
> +free_cmap:
> + free_percpu(cmap->flush_needed);
> + kfree(cmap);
> + return ERR_PTR(err);
> +}