bpf: Introduce internal bpf_map_check_op_flags helper function

It is to unify map flags checking for lookup_elem, update_elem,
lookup_batch and update_batch APIs.

Therefore, it will be convenient to check BPF_F_CPU and BPF_F_ALL_CPUS
flags in it for these APIs in next patch.

Acked-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Leon Hwang <[email protected]>

Author: Asphaltt

include/linux/bpf.h

@@ -3768,4 +3768,15 @@ int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char *
 			   const char **linep, int *nump);
 struct bpf_prog *bpf_prog_find_from_stack(void);
 
+static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 allowed_flags)
+{
+	if (flags & ~allowed_flags)
+		return -EINVAL;
+
+	if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK))
+		return -EINVAL;
+
+	return 0;
+}
+
 #endif /* _LINUX_BPF_H */

kernel/bpf/syscall.c

@@ -1708,19 +1708,16 @@ static int map_lookup_elem(union bpf_attr *attr)
 	if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
 		return -EINVAL;
 
-	if (attr->flags & ~BPF_F_LOCK)
-		return -EINVAL;
-
 	CLASS(fd, f)(attr->map_fd);
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 	if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ))
 		return -EPERM;
 
-	if ((attr->flags & BPF_F_LOCK) &&
-	    !btf_record_has_field(map->record, BPF_SPIN_LOCK))
-		return -EINVAL;
+	err = bpf_map_check_op_flags(map, attr->flags, BPF_F_LOCK);
+	if (err)
+		return err;
 
 	key = __bpf_copy_key(ukey, map->key_size);
 	if (IS_ERR(key))
@@ -1783,11 +1780,9 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
 		goto err_put;
 	}
 
-	if ((attr->flags & BPF_F_LOCK) &&
-	    !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
-		err = -EINVAL;
+	err = bpf_map_check_op_flags(map, attr->flags, ~0);
+	if (err)
 		goto err_put;
-	}
 
 	key = ___bpf_copy_key(ukey, map->key_size);
 	if (IS_ERR(key)) {
@@ -1991,13 +1986,9 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
 	void *key, *value;
 	int err = 0;
 
-	if (attr->batch.elem_flags & ~BPF_F_LOCK)
-		return -EINVAL;
-
-	if ((attr->batch.elem_flags & BPF_F_LOCK) &&
-	    !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
-		return -EINVAL;
-	}
+	err = bpf_map_check_op_flags(map, attr->batch.elem_flags, BPF_F_LOCK);
+	if (err)
+		return err;
 
 	value_size = bpf_map_value_size(map);
 
@@ -2054,12 +2045,9 @@ int generic_map_lookup_batch(struct bpf_map *map,
 	u32 value_size, cp, max_count;
 	int err;
 
-	if (attr->batch.elem_flags & ~BPF_F_LOCK)
-		return -EINVAL;
-
-	if ((attr->batch.elem_flags & BPF_F_LOCK) &&
-	    !btf_record_has_field(map->record, BPF_SPIN_LOCK))
-		return -EINVAL;
+	err = bpf_map_check_op_flags(map, attr->batch.elem_flags, BPF_F_LOCK);
+	if (err)
+		return err;
 
 	value_size = bpf_map_value_size(map);