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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c2966159c07sm441454566b.63.2026.09.14.06.35.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 06:35:11 -0700 (PDT) From: David Carlier To: rostedt@goodmis.org, mhiramat@kernel.org Cc: mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, David Carlier , stable@vger.kernel.org, Sashiko Subject: [PATCH v2 2/2] ring-buffer: Do not show buffer_meta for CPUs without a buffer Date: Mon, 14 Sep 2026 14:35:05 +0100 Message-ID: <20260914133506.4865-3-devnexen@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260914133506.4865-1-devnexen@gmail.com> References: <20260914133506.4865-1-devnexen@gmail.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The per_cpu/cpuN/buffer_meta files are created for every possible CPU, but buffer->buffers[cpu] is only allocated once that CPU comes online. Reading the file of a CPU that never came online dereferences a NULL cpu_buffer in rbm_start(). Fail the open with -ENODEV when the CPU has no buffer, as the other per CPU ring buffer interfaces do. Cc: stable@vger.kernel.org Fixes: 950032ffcee7 ("ring-buffer: Add output of ring buffer meta page") Reported-by: Sashiko Closes: https://lore.kernel.org/all/20260913134906.6E8A01F000FF@smtp.kernel.org/ Signed-off-by: David Carlier --- kernel/trace/ring_buffer.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 9c03a555a6ba..8833d04b9fee 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2381,6 +2381,9 @@ int ring_buffer_meta_seq_init(struct file *file, struct trace_buffer *buffer, in struct seq_file *m; int ret; + if (!cpumask_test_cpu(cpu, buffer->cpumask)) + return -ENODEV; + ret = seq_open(file, &rb_meta_seq_ops); if (ret) return ret; -- 2.55.0