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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6aa1d25e331sm2303248a12.17.2026.09.16.12.26.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Sep 2026 12:26:31 -0700 (PDT) From: David Carlier To: rostedt@goodmis.org, mhiramat@kernel.org Cc: vdonnefort@google.com, mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, David Carlier Subject: [PATCH v2] ring-buffer: Take cpus_read_lock() when changing the subbuf order Date: Wed, 16 Sep 2026 20:26:28 +0100 Message-ID: <20260916192628.274136-1-devnexen@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260914182850.21449-1-devnexen@gmail.com> References: <20260914182850.21449-1-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 A CPU coming online for the first time gets its per CPU buffer allocated by trace_rb_cpu_prepare(), which then adds it to buffer->cpumask. If that happens while ring_buffer_subbuf_order_set() is running, the CPU shows up after the allocation loop and the install loop walks it with an empty new_pages list, corrupting the buffer. Take cpus_read_lock() as ring_buffer_resize() does. Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page") Cc: stable@vger.kernel.org Signed-off-by: David Carlier --- Notes: v2: - Reword the changelog: offlined CPUs stay in ->cpumask, so only a CPU coming online for the first time can appear mid-flight (Vincent) - Drop the comment above guard(cpus_read_lock)() (Vincent) v1: https://lore.kernel.org/linux-trace-kernel/20260914182850.21449-1-devnexen@gmail.com/ kernel/trace/ring_buffer.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 04bb94c29f58..e78fb4bb2195 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -7464,6 +7464,8 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) if (psize > RB_WRITE_MASK + 1) return -EINVAL; + guard(cpus_read_lock)(); + /* prevent another thread from changing buffer sizes */ guard(mutex)(&buffer->mutex); -- 2.55.0