* [for-next][PATCH 5/5] ring-buffer: Take cpus_read_lock() when changing the subbuf order
[not found] <20261019193330.365764549@kernel.org>
@ 2026-10-19 19:33 ` Steven Rostedt
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From: Steven Rostedt @ 2026-10-19 19:33 UTC (permalink / raw)
To: linux-kernel
Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton,
stable, David Carlier, Vincent Donnefort
From: David Carlier <devnexen@gmail.com>
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 <devnexen@gmail.com>
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
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);
--
2.53.0
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