BTF_TYPE_SAFE_TRUSTED(struct bpf_iter__task) in verifier.c wanted to teach BPF verifier that bpf_iter__task -> task is a trusted ptr. But it doesn't work well. The reason is, bpf_iter__task -> task would go through btf_ctx_access() which enforces the reg_type of 'task' is ctx_arg_info->reg_type, and in task_iter.c, we actually explicitly declare that the ctx_arg_info->reg_type is PTR_TO_BTF_ID_OR_NULL. Actually we have a previous case like this[1] where PTR_TRUSTED is added to the arg flag for map_iter. This patch sets ctx_arg_info->reg_type is PTR_TO_BTF_ID_OR_NULL | PTR_TRUSTED in task_reg_info. Similarly, bpf_cgroup_reg_info -> cgroup is also PTR_TRUSTED since we are under the protection of cgroup_mutex and we would check cgroup_is_dead() in __cgroup_iter_seq_show(). Link[1]:https://lore.kernel.org/all/20230706133932.45883-3-aspsk@xxxxxxxxxxxxx/ Signed-off-by: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx> Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx> --- kernel/bpf/cgroup_iter.c | 2 +- kernel/bpf/task_iter.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/cgroup_iter.c b/kernel/bpf/cgroup_iter.c index d1b5c5618..f04a468cf 100644 --- a/kernel/bpf/cgroup_iter.c +++ b/kernel/bpf/cgroup_iter.c @@ -282,7 +282,7 @@ static struct bpf_iter_reg bpf_cgroup_reg_info = { .ctx_arg_info_size = 1, .ctx_arg_info = { { offsetof(struct bpf_iter__cgroup, cgroup), - PTR_TO_BTF_ID_OR_NULL }, + PTR_TO_BTF_ID_OR_NULL | PTR_TRUSTED }, }, .seq_info = &cgroup_iter_seq_info, }; diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 4e156dca4..26082b978 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -704,7 +704,7 @@ static struct bpf_iter_reg task_reg_info = { .ctx_arg_info_size = 1, .ctx_arg_info = { { offsetof(struct bpf_iter__task, task), - PTR_TO_BTF_ID_OR_NULL }, + PTR_TO_BTF_ID_OR_NULL | PTR_TRUSTED }, }, .seq_info = &task_seq_info, .fill_link_info = bpf_iter_fill_link_info, -- 2.20.1
