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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c296614b29bsm467316666b.62.2026.09.14.11.28.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 11:28:54 -0700 (PDT) From: David Carlier To: rostedt@goodmis.org, mhiramat@kernel.org Cc: mathieu.desnoyers@efficios.com, vdonnefort@google.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, David Carlier , stable@vger.kernel.org Subject: [PATCH] ring-buffer: Take cpus_read_lock() when changing the subbuf order Date: Mon, 14 Sep 2026 19:28:43 +0100 Message-ID: <20260914182850.21449-1-devnexen@gmail.com> X-Mailer: git-send-email 2.55.0 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 during ring_buffer_subbuf_order_set() can be added to buffer->cpumask after the allocation loop, and the install loop then uses its 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 --- kernel/trace/ring_buffer.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 04bb94c29f58..445931bc9ae0 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -7464,6 +7464,12 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) if (psize > RB_WRITE_MASK + 1) return -EINVAL; + /* + * Keep CPUs from coming online while changing the order to + * synchronize with new per CPU buffers being created. + */ + guard(cpus_read_lock)(); + /* prevent another thread from changing buffer sizes */ guard(mutex)(&buffer->mutex); -- 2.55.0