Hello, Alexei.
在 2023/9/13 01:13, Alexei Starovoitov 写道:
On Tue, Sep 12, 2023 at 03:01:45PM +0800, Chuyi Zhou wrote:
This patch adds kfuncs bpf_iter_css_task_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_css_task in open-coded
iterator style. These kfuncs actually wrapps css_task_iter_{start,next,
end}. BPF programs can use these kfuncs through bpf_for_each macro for
iteration of all tasks under a css.
css_task_iter_*() would try to get the global spin-lock *css_set_lock*, so
the bpf side has to be careful in where it allows to use this iter.
Currently we only allow it in bpf_lsm and bpf iter-s.
Signed-off-by: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>
---
include/uapi/linux/bpf.h | 4 +++
kernel/bpf/helpers.c | 3 +++
kernel/bpf/task_iter.c | 48 ++++++++++++++++++++++++++++++++++
kernel/bpf/verifier.c | 23 ++++++++++++++++
tools/include/uapi/linux/bpf.h | 4 +++
tools/lib/bpf/bpf_helpers.h | 7 +++++
6 files changed, 89 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 73b155e52204..de02c0971428 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -7318,4 +7318,8 @@ struct bpf_iter_num {
__u64 __opaque[1];
} __attribute__((aligned(8)));
+struct bpf_iter_css_task {
+ __u64 __opaque[1];
+} __attribute__((aligned(8)));
+
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index b0a9834f1051..d6a16becfbb9 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2504,6 +2504,9 @@ BTF_ID_FLAGS(func, bpf_dynptr_slice_rdwr, KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_num_new, KF_ITER_NEW)
BTF_ID_FLAGS(func, bpf_iter_num_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_iter_css_task_new, KF_ITER_NEW)
Looking at selftest:
struct cgroup_subsys_state *css = &cgrp->self;
realized that we're missing KF_TRUSTED_ARGS here.
+BTF_ID_FLAGS(func, bpf_iter_css_task_next, KF_ITER_NEXT | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_iter_css_task_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_dynptr_adjust)
BTF_ID_FLAGS(func, bpf_dynptr_is_null)
BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index 7473068ed313..d8539cc05ffd 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -803,6 +803,54 @@ const struct bpf_func_proto bpf_find_vma_proto = {
.arg5_type = ARG_ANYTHING,
};
+struct bpf_iter_css_task_kern {
+ struct css_task_iter *css_it;
+} __attribute__((aligned(8)));
+
+__bpf_kfunc int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
+ struct cgroup_subsys_state *css, unsigned int flags)
the verifier does a type check, but it's not strong enough.
We need KF_TRUSTED_ARGS to make sure the pointer is valid.
The BTF_TYPE_SAFE_RCU(struct cgroup) {
probably doesn't need to change, since '&cgrp->self' is not a pointer deref.
The verifier should understand that cgroup_subsys_state is also PTR_TRUSTED
just like 'cgrp' pointer.
Got it. It seems we should also apply this to bpf_iter_css_{pre,post}_new.
Also please add negative tests in patch 6.
Like doing bpf_rcu_read_unlock() in the middle and check that the verifier
catches such mistake.
I will do it in next version.
Thanks.
