linux-kernel - [PATCH bpf-next v5 2/2] bpf: allow bpf_current_task_under_cgroup() with BPF_CGROUP

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Message-ID: <20240813132831.184362-3-technoboy85@gmail.com>
Date: Tue, 13 Aug 2024 15:28:31 +0200
From: Matteo Croce <technoboy85@...il.com>
To: Andrii Nakryiko <andrii@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	bpf@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Matteo Croce <teknoraver@...a.com>
Subject: [PATCH bpf-next v5 2/2] bpf: allow bpf_current_task_under_cgroup() with BPF_CGROUP_*

From: Matteo Croce <teknoraver@...a.com>

The helper bpf_current_task_under_cgroup() currently is only allowed for
tracing programs, allow its usage also in the BPF_CGROUP_* program types.

Move the code from kernel/trace/bpf_trace.c to kernel/bpf/helpers.c,
so it compiles also without CONFIG_BPF_EVENTS.

This will be used in systemd-networkd to monitor the sysctl writes,
and filter it's own writes from others:
https://github.com/systemd/systemd/pull/32212

Signed-off-by: Matteo Croce <teknoraver@...a.com>
---
 include/linux/bpf.h      |  1 +
 kernel/bpf/cgroup.c      |  2 ++
 kernel/bpf/helpers.c     | 23 +++++++++++++++++++++++
 kernel/trace/bpf_trace.c | 23 -----------------------
 4 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b9425e410bcb..f0192c173ed8 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3206,6 +3206,7 @@ extern const struct bpf_func_proto bpf_sock_hash_update_proto;
 extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;
 extern const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto;
 extern const struct bpf_func_proto bpf_get_cgroup_classid_curr_proto;
+extern const struct bpf_func_proto bpf_current_task_under_cgroup_proto;
 extern const struct bpf_func_proto bpf_msg_redirect_hash_proto;
 extern const struct bpf_func_proto bpf_msg_redirect_map_proto;
 extern const struct bpf_func_proto bpf_sk_redirect_hash_proto;
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 8ba73042a239..e7113d700b87 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -2581,6 +2581,8 @@ cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_cgroup_classid:
 		return &bpf_get_cgroup_classid_curr_proto;
 #endif
+	case BPF_FUNC_current_task_under_cgroup:
+		return &bpf_current_task_under_cgroup_proto;
 	default:
 		return NULL;
 	}
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 0d1d97d968b0..8502cfed2926 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2458,6 +2458,29 @@ __bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task,
 	return ret;
 }
 
+BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)
+{
+	struct bpf_array *array = container_of(map, struct bpf_array, map);
+	struct cgroup *cgrp;
+
+	if (unlikely(idx >= array->map.max_entries))
+		return -E2BIG;
+
+	cgrp = READ_ONCE(array->ptrs[idx]);
+	if (unlikely(!cgrp))
+		return -EAGAIN;
+
+	return task_under_cgroup_hierarchy(current, cgrp);
+}
+
+const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {
+	.func           = bpf_current_task_under_cgroup,
+	.gpl_only       = false,
+	.ret_type       = RET_INTEGER,
+	.arg1_type      = ARG_CONST_MAP_PTR,
+	.arg2_type      = ARG_ANYTHING,
+};
+
 /**
  * bpf_task_get_cgroup1 - Acquires the associated cgroup of a task within a
  * specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d557bb11e0ff..e4e1f5d8b2a6 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -797,29 +797,6 @@ const struct bpf_func_proto bpf_task_pt_regs_proto = {
 	.ret_btf_id	= &bpf_task_pt_regs_ids[0],
 };
 
-BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)
-{
-	struct bpf_array *array = container_of(map, struct bpf_array, map);
-	struct cgroup *cgrp;
-
-	if (unlikely(idx >= array->map.max_entries))
-		return -E2BIG;
-
-	cgrp = READ_ONCE(array->ptrs[idx]);
-	if (unlikely(!cgrp))
-		return -EAGAIN;
-
-	return task_under_cgroup_hierarchy(current, cgrp);
-}
-
-static const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {
-	.func           = bpf_current_task_under_cgroup,
-	.gpl_only       = false,
-	.ret_type       = RET_INTEGER,
-	.arg1_type      = ARG_CONST_MAP_PTR,
-	.arg2_type      = ARG_ANYTHING,
-};
-
 struct send_signal_irq_work {
 	struct irq_work irq_work;
 	struct task_struct *task;
-- 
2.46.0