On 10/06/2017 06:12 PM, Jesper Dangaard Brouer wrote:
[...]
+static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
+{
+ struct bpf_cpu_map *cmap;
+ int err = -ENOMEM;
err init here is basically not needed since overriden later anyway
w/o being read, but ...
+ u64 cost;
+
+ 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)
Nit: needs to be >= NR_CPUS.
+ return ERR_PTR(-E2BIG);
+
+ /* 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 */
+ err = bpf_map_precharge_memlock(cmap->map.pages);
+ if (err)
+ goto free_cmap;
... here, you need to set err = -ENOMEM.
+ /* 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;
Otherwise when we fail here or in error case for bpf_map_area_alloc()
below, we still return 0 although it's really -ENOMEM. And returning 0,
would mean that find_and_alloc_map() will miss this since it only tests
for IS_ERR(), and we'll crash later on thinking we have a valid map
pointer.
+ /* 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);
+}
+
[...]
+int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
+ u64 map_flags)
+{
+ struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
+ struct bpf_cpu_map_entry *rcpu;
+
+ /* Array index key correspond to CPU number */
+ u32 key_cpu = *(u32 *)key;
+ /* Value is the queue size */
+ u32 qsize = *(u32 *)value;
+
+ /* Make sure CPU is a valid possible cpu */
+ if (!cpu_possible(key_cpu))
+ return -ENODEV;
Nit: cpu_possible() expects that key_cpu < NR_CPUS, otherwise you'd
access the bitmap out of bounds.
Better move the below test for 'key_cpu >= cmap->map.max_entries'
first as on map alloc you enforce upper limit of NR_CPUS on the
max_entries, then above cpu_possible() test will be valid, too.
+ if (unlikely(map_flags > BPF_EXIST))
+ return -EINVAL;
+ if (unlikely(key_cpu >= cmap->map.max_entries))
+ return -E2BIG;
+ if (unlikely(map_flags == BPF_NOEXIST))
+ return -EEXIST;
+ if (unlikely(qsize > 16384)) /* sanity limit on qsize */
+ return -EOVERFLOW;
+
+ if (qsize == 0) {
+ rcpu = NULL; /* Same as deleting */
+ } else {
+ /* Updating qsize cause re-allocation of bpf_cpu_map_entry */
+ rcpu = __cpu_map_entry_alloc(qsize, key_cpu, map->id);
+ if (!rcpu)
+ return -ENOMEM;
+ }
+ rcu_read_lock();
+ __cpu_map_entry_replace(cmap, key_cpu, rcpu);
+ rcu_read_unlock();
+ return 0;
+}
[...]
+struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
+{
+ struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
+ struct bpf_cpu_map_entry *rcpu;
+
+ if (key >= map->max_entries)
+ return NULL;
+
+ rcpu = READ_ONCE(cmap->cpu_map[key]);
+ return rcpu;
+}
+
+static void *cpu_map_lookup_elem(struct bpf_map *map, void *key)
+{
+ struct bpf_cpu_map_entry *rcpu =
+ __cpu_map_lookup_elem(map, *(u32 *)key);
+
+ return rcpu ? &rcpu->qsize : NULL;
I still think from my prior email/comment that we should use per-cpu
scratch buffer here. Would be nice to keep the guarantee that noone
can modify it, it's just a tiny change.
+}
+
+static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
+{
+ struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
+ u32 index = key ? *(u32 *)key : U32_MAX;
+ u32 *next = next_key;
+
+ if (index >= cmap->map.max_entries) {
+ *next = 0;
+ return 0;
+ }
+
+ if (index == cmap->map.max_entries - 1)
+ return -ENOENT;
+ *next = index + 1;
+ return 0;
+}
+
+const struct bpf_map_ops cpu_map_ops = {
+ .map_alloc = cpu_map_alloc,
+ .map_free = cpu_map_free,
+ .map_delete_elem = cpu_map_delete_elem,
+ .map_update_elem = cpu_map_update_elem,
+ .map_lookup_elem = cpu_map_lookup_elem,
+ .map_get_next_key = cpu_map_get_next_key,
+};
