Merge branch 'bpf-fixes-for-maybe_wait_bpf_programs'

Hou Tao says:

====================
The patch set aims to fix the problems found when inspecting the code
related with maybe_wait_bpf_programs().

Patch #1 removes unnecessary invocation of maybe_wait_bpf_programs().
Patch #2 calls maybe_wait_bpf_programs() only once for batched update.
Patch #3 adds the missed waiting when doing batched lookup_deletion on
htab of maps. Patch #4 does wait only if the update or deletion
operation succeeds. Patch #5 fixes the value of batch.count when memory
allocation fails.
====================

Link: https://lore.kernel.org/r/20231208102355.2628918-1-houtao@huaweicloud.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/syscall.c

@@ -203,7 +203,6 @@ static int bpf_map_update_value(struct bpf_map *map, struct file *map_file,
 		rcu_read_unlock();
 	}
 	bpf_enable_instrumentation();
-	maybe_wait_bpf_programs(map);
 
 	return err;
 }
@@ -264,7 +263,6 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value,
 	}
 
 	bpf_enable_instrumentation();
-	maybe_wait_bpf_programs(map);
 
 	return err;
 }
@@ -1578,6 +1576,8 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
 	}
 
 	err = bpf_map_update_value(map, f.file, key, value, attr->flags);
+	if (!err)
+		maybe_wait_bpf_programs(map);
 
 	kvfree(value);
 free_key:
@@ -1633,7 +1633,8 @@ static int map_delete_elem(union bpf_attr *attr, bpfptr_t uattr)
 	err = map->ops->map_delete_elem(map, key);
 	rcu_read_unlock();
 	bpf_enable_instrumentation();
-	maybe_wait_bpf_programs(map);
+	if (!err)
+		maybe_wait_bpf_programs(map);
 out:
 	kvfree(key);
 err_put:
@@ -1730,6 +1731,9 @@ int generic_map_delete_batch(struct bpf_map *map,
 	if (!max_count)
 		return 0;
 
+	if (put_user(0, &uattr->batch.count))
+		return -EFAULT;
+
 	key = kvmalloc(map->key_size, GFP_USER | __GFP_NOWARN);
 	if (!key)
 		return -ENOMEM;
@@ -1759,7 +1763,6 @@ int generic_map_delete_batch(struct bpf_map *map,
 
 	kvfree(key);
 
-	maybe_wait_bpf_programs(map);
 	return err;
 }
 
@@ -1787,6 +1790,9 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
 	if (!max_count)
 		return 0;
 
+	if (put_user(0, &uattr->batch.count))
+		return -EFAULT;
+
 	key = kvmalloc(map->key_size, GFP_USER | __GFP_NOWARN);
 	if (!key)
 		return -ENOMEM;
@@ -1817,6 +1823,7 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
 
 	kvfree(value);
 	kvfree(key);
+
 	return err;
 }
 
@@ -5030,8 +5037,10 @@ static int bpf_map_do_batch(const union bpf_attr *attr,
 	else
 		BPF_DO_BATCH(map->ops->map_delete_batch, map, attr, uattr);
 err_put:
-	if (has_write)
+	if (has_write) {
+		maybe_wait_bpf_programs(map);
 		bpf_map_write_active_dec(map);
+	}
 	fdput(f);
 	return err;
 }