From 0de4f50de25af79c2a46db55d70cdbd8f985c6d1 Mon Sep 17 00:00:00 2001 From: Chuyi Zhou Date: Tue, 7 Nov 2023 21:22:03 +0800 Subject: [PATCH] bpf: Let verifier consider {task,cgroup} is trusted in bpf_iter_reg 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(). This patch is to improve the user experience of the newly introduced bpf_iter_css_task kfunc before hitting the mainline. The Fixes tag is pointing to the commit introduced the bpf_iter_css_task kfunc. Link[1]:https://lore.kernel.org/all/20230706133932.45883-3-aspsk@isovalent.com/ Fixes: 9c66dc94b62a ("bpf: Introduce css_task open-coded iterator kfuncs") Signed-off-by: Chuyi Zhou Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20231107132204.912120-2-zhouchuyi@bytedance.com Signed-off-by: Martin KaFai Lau --- 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 d1b5c5618dd7..f04a468cf6a7 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 4e156dca48de..26082b97894d 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,