From: Ning Ding <dingning04@gmail.com>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Emil Tsalapatis <emil@etsalapatis.com>,
Ihor Solodrai <ihor.solodrai@linux.dev>,
Shuah Khan <shuah@kernel.org>, Ning Ding <dingning04@gmail.com>,
Chuyi Zhou <zhouchuyi@bytedance.com>,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: [PATCH bpf-next v2 2/2] selftests/bpf: Test RCU iterator state pruning
Date: Mon, 10 Aug 2026 20:59:55 -0700 [thread overview]
Message-ID: <20260811035955.132989-3-dingning04@gmail.com> (raw)
In-Reply-To: <20260811035955.132989-1-dingning04@gmail.com>
Add a path where RCU protection reaches zero and then starts again.
The iterator is untrusted after this gap and must be rejected.
Signed-off-by: Ning Ding <dingning04@gmail.com>
---
.../selftests/bpf/progs/iters_task_failure.c | 46 +++++++++++++++++++
1 file changed, 46 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/iters_task_failure.c b/tools/testing/selftests/bpf/progs/iters_task_failure.c
index fe3663dedbe14..566a1d3dffeab 100644
--- a/tools/testing/selftests/bpf/progs/iters_task_failure.c
+++ b/tools/testing/selftests/bpf/progs/iters_task_failure.c
@@ -61,6 +61,52 @@ int BPF_PROG(iter_tasks_lock_and_unlock)
return 0;
}
+SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
+__failure __msg("expected an RCU CS when using bpf_iter_task_next")
+__flag(BPF_F_TEST_STATE_FREQ)
+int BPF_PROG(iter_tasks_rcu_state_pruning)
+{
+ struct bpf_iter_task it;
+
+ asm volatile (
+ "call %[bpf_rcu_read_lock];"
+ "r1 = %[it];"
+ "r2 = 0;"
+ "r3 = 0;" /* BPF_TASK_ITER_ALL_PROCS */
+ "call %[bpf_iter_task_new];"
+
+ "call %[bpf_get_prandom_u32];"
+ "if w0 == 0 goto unprotected_%=;"
+
+ /* Keep the outer RCU lock active on the straight-line path. */
+ "call %[bpf_rcu_read_lock];"
+ "call %[bpf_rcu_read_unlock];"
+ "goto merge_%=;"
+
+ "unprotected_%=:"
+ /* Create an unprotected gap on the taken path. */
+ "call %[bpf_rcu_read_unlock];"
+ "call %[bpf_rcu_read_lock];"
+
+ "merge_%=: r1 = %[it];"
+ "call %[bpf_iter_task_next];"
+ "r1 = %[it];"
+ "call %[bpf_iter_task_destroy];"
+ "call %[bpf_rcu_read_unlock];"
+ :
+ : __imm_ptr(it),
+ __imm(bpf_get_prandom_u32),
+ __imm(bpf_iter_task_new),
+ __imm(bpf_iter_task_next),
+ __imm(bpf_iter_task_destroy),
+ __imm(bpf_rcu_read_lock),
+ __imm(bpf_rcu_read_unlock)
+ : __clobber_common
+ );
+
+ return 0;
+}
+
SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
__failure __msg("expected an RCU CS when using bpf_iter_css_next")
int BPF_PROG(iter_css_lock_and_unlock)
--
2.43.0
next prev parent reply other threads:[~2026-08-11 4:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-11 3:59 [PATCH bpf-next v2 0/2] bpf: Compare iterator types during state pruning Ning Ding
2026-08-11 3:59 ` [PATCH bpf-next v2 1/2] " Ning Ding
2026-08-11 3:59 ` Ning Ding [this message]
2026-08-11 4:41 ` [PATCH bpf-next v2 2/2] selftests/bpf: Test RCU iterator " bot+bpf-ci
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