bpf: hashtab: move checks out of alloc function

Use the new callback to perform allocation checks for hash maps.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

kernel/bpf/hashtab.c

@@ -227,7 +227,7 @@ static int alloc_extra_elems(struct bpf_htab *htab)
 }
 
 /* Called from syscall */
-static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
+static int htab_map_alloc_check(union bpf_attr *attr)
 {
 	bool percpu = (attr->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
 		       attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
@@ -241,9 +241,6 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 	bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
 	bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
 	int numa_node = bpf_map_attr_numa_node(attr);
-	struct bpf_htab *htab;
-	int err, i;
-	u64 cost;
 
 	BUILD_BUG_ON(offsetof(struct htab_elem, htab) !=
 		     offsetof(struct htab_elem, hash_node.pprev));
@@ -254,33 +251,33 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 		/* LRU implementation is much complicated than other
 		 * maps.  Hence, limit to CAP_SYS_ADMIN for now.
 		 */
-		return ERR_PTR(-EPERM);
+		return -EPERM;
 
 	if (attr->map_flags & ~HTAB_CREATE_FLAG_MASK)
 		/* reserved bits should not be used */
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 
 	if (!lru && percpu_lru)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 
 	if (lru && !prealloc)
-		return ERR_PTR(-ENOTSUPP);
+		return -ENOTSUPP;
 
 	if (numa_node != NUMA_NO_NODE && (percpu || percpu_lru))
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 
 	/* check sanity of attributes.
 	 * value_size == 0 may be allowed in the future to use map as a set
 	 */
 	if (attr->max_entries == 0 || attr->key_size == 0 ||
 	    attr->value_size == 0)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 
 	if (attr->key_size > MAX_BPF_STACK)
 		/* eBPF programs initialize keys on stack, so they cannot be
 		 * larger than max stack size
 		 */
-		return ERR_PTR(-E2BIG);
+		return -E2BIG;
 
 	if (attr->value_size >= KMALLOC_MAX_SIZE -
 	    MAX_BPF_STACK - sizeof(struct htab_elem))
@@ -289,7 +286,28 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 		 * sure that the elem_size doesn't overflow and it's
 		 * kmalloc-able later in htab_map_update_elem()
 		 */
-		return ERR_PTR(-E2BIG);
+		return -E2BIG;
+
+	return 0;
+}
+
+static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
+{
+	bool percpu = (attr->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
+		       attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
+	bool lru = (attr->map_type == BPF_MAP_TYPE_LRU_HASH ||
+		    attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
+	/* percpu_lru means each cpu has its own LRU list.
+	 * it is different from BPF_MAP_TYPE_PERCPU_HASH where
+	 * the map's value itself is percpu.  percpu_lru has
+	 * nothing to do with the map's value.
+	 */
+	bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
+	bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
+	int numa_node = bpf_map_attr_numa_node(attr);
+	struct bpf_htab *htab;
+	int err, i;
+	u64 cost;
 
 	htab = kzalloc(sizeof(*htab), GFP_USER);
 	if (!htab)
@@ -1142,6 +1160,7 @@ static void htab_map_free(struct bpf_map *map)
 }
 
 const struct bpf_map_ops htab_map_ops = {
+	.map_alloc_check = htab_map_alloc_check,
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1152,6 +1171,7 @@ const struct bpf_map_ops htab_map_ops = {
 };
 
 const struct bpf_map_ops htab_lru_map_ops = {
+	.map_alloc_check = htab_map_alloc_check,
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1235,6 +1255,7 @@ int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
 }
 
 const struct bpf_map_ops htab_percpu_map_ops = {
+	.map_alloc_check = htab_map_alloc_check,
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1244,6 +1265,7 @@ const struct bpf_map_ops htab_percpu_map_ops = {
 };
 
 const struct bpf_map_ops htab_lru_percpu_map_ops = {
+	.map_alloc_check = htab_map_alloc_check,
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
@@ -1252,11 +1274,11 @@ const struct bpf_map_ops htab_lru_percpu_map_ops = {
 	.map_delete_elem = htab_lru_map_delete_elem,
 };
 
-static struct bpf_map *fd_htab_map_alloc(union bpf_attr *attr)
+static int fd_htab_map_alloc_check(union bpf_attr *attr)
 {
 	if (attr->value_size != sizeof(u32))
-		return ERR_PTR(-EINVAL);
-	return htab_map_alloc(attr);
+		return -EINVAL;
+	return htab_map_alloc_check(attr);
 }
 
 static void fd_htab_map_free(struct bpf_map *map)
@@ -1327,7 +1349,7 @@ static struct bpf_map *htab_of_map_alloc(union bpf_attr *attr)
 	if (IS_ERR(inner_map_meta))
 		return inner_map_meta;
 
-	map = fd_htab_map_alloc(attr);
+	map = htab_map_alloc(attr);
 	if (IS_ERR(map)) {
 		bpf_map_meta_free(inner_map_meta);
 		return map;
@@ -1371,6 +1393,7 @@ static void htab_of_map_free(struct bpf_map *map)
 }
 
 const struct bpf_map_ops htab_of_maps_map_ops = {
+	.map_alloc_check = fd_htab_map_alloc_check,
 	.map_alloc = htab_of_map_alloc,
 	.map_free = htab_of_map_free,
 	.map_get_next_key = htab_map_get_next_key,