From 453d0f47b174cac387af48d303c503b84f82212e Mon Sep 17 00:00:00 2001 From: David Carlier Date: Wed, 16 Sep 2026 20:26:28 +0100 Subject: [PATCH] ring-buffer: Take cpus_read_lock() when changing the subbuf order 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. Cc: stable@vger.kernel.org Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page") Link: https://patch.msgid.link/20260916192628.274136-1-devnexen@gmail.com Signed-off-by: David Carlier Reviewed-by: Vincent Donnefort Signed-off-by: Steven Rostedt --- 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 0068bd185945..443271779e94 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);