Re: [net-next V8 PATCH 1/5] bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP

On Mon, 16 Oct 2017 12:19:28 +0200 Jesper Dangaard Brouer [off-list ref] wrote:

+static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
+{
+	struct bpf_cpu_map *cmap;
+	int err = -ENOMEM;

Notice err is set to -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) {
+		err = -E2BIG;
+		goto free_cmap;
+	}
+
+	/* 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 */

[... continued below ...]

On Wed, 18 Oct 2017 09:45:59 +0200 Yann Ylavic [off-list ref] wrote:

On Mon, Oct 16, 2017 at 12:19 PM, Jesper Dangaard Brouer
[off-list ref] wrote:

quoted

+
+       /* 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)  

ret = -ENOMEM; ?

Did you notice that "err" already is = -ENOMEM at this point?

quoted

+               goto free_percpu;
+
+       return &cmap->map;
+free_percpu:
+       free_percpu(cmap->flush_needed);
+free_cmap:
+       kfree(cmap);
+       return ERR_PTR(err);
+}  

Regards,
Yann.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer