Re: [PATCH bpf-next] bpf: Use struct_size() helper
From: Yonghong Song <hidden>
Date: 2021-12-20 16:20:32
Also in:
bpf, lkml
On 12/20/21 3:30 AM, Xiu Jianfeng wrote:
In an effort to avoid open-coded arithmetic in the kernel, use the struct_size() helper instead of open-coded calculation. Link: https://github.com/KSPP/linux/issues/160 Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Ack with a minor comments below. Acked-by: Yonghong Song <redacted>
quoted hunk ↗ jump to hunk
--- kernel/bpf/local_storage.c | 3 +-- kernel/bpf/reuseport_array.c | 6 +----- 2 files changed, 2 insertions(+), 7 deletions(-)diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c index 035e9e3a7132..23f7f9d08a62 100644 --- a/kernel/bpf/local_storage.c +++ b/kernel/bpf/local_storage.c@@ -163,8 +163,7 @@ static int cgroup_storage_update_elem(struct bpf_map *map, void *key, return 0; } - new = bpf_map_kmalloc_node(map, sizeof(struct bpf_storage_buffer) + - map->value_size, + new = bpf_map_kmalloc_node(map, struct_size(new, data, map->value_size), __GFP_ZERO | GFP_ATOMIC | __GFP_NOWARN, map->numa_node); if (!new)diff --git a/kernel/bpf/reuseport_array.c b/kernel/bpf/reuseport_array.c index 93a55391791a..556a769b5b80 100644 --- a/kernel/bpf/reuseport_array.c +++ b/kernel/bpf/reuseport_array.c@@ -152,16 +152,12 @@ static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr) { int numa_node = bpf_map_attr_numa_node(attr); struct reuseport_array *array; - u64 array_size; if (!bpf_capable()) return ERR_PTR(-EPERM); - array_size = sizeof(*array); - array_size += (u64)attr->max_entries * sizeof(struct sock *);
We have u64 type conversion here while struct_size used type 'size_t'.
So we won't have problems for 64bit system. But for 32bit system, we may
have a slight different behavior here as the current code can return a
u64 value and the struct_size(...) returns a size_t type value with max
value SIZE_MAX.
In __bpf_map_area_alloc() we have a check:
if (size >= SIZE_MAX)
return NULL;
so we should be fine for 32bit system.
- /* allocate all map elements and zero-initialize them */ - array = bpf_map_area_alloc(array_size, numa_node); + array = bpf_map_area_alloc(struct_size(array, ptrs, attr->max_entries), numa_node); if (!array) return ERR_PTR(-ENOMEM);