[PATCH v5 03/10] ring-buffer: Make cpu_buffer::free_page a buffer_data_read_page
From: Vincent Donnefort <hidden>
Date: 2026-08-13 13:12:01
Also in:
lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Discarding a cached reader page after a concurrent ring buffer resize
uses the new global subbuf_order for the free_pages() call. This
mismatched order may crashes the kernel or leaks memory because the cached
page was allocated under the old size.
Save the actual free_page order alongside the page address to ensure we
always refer to the correct value and do not rely on the potentially
stalled cpu_buffer->subbuf_order value. The simplest is to make
free_page a buffer_data_read_page which already covers exactly what we
need: a page address and a page order.
Fixes: 8e7b58c27b3c ("ring-buffer: Just update the subbuffers when changing their allocation order")
Signed-off-by: Vincent Donnefort <redacted>
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index ec4f5a0c93e8..b6fa258aafe2 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c@@ -507,7 +507,7 @@ struct ring_buffer_per_cpu { raw_spinlock_t reader_lock; /* serialize readers */ arch_spinlock_t lock; struct lock_class_key lock_key; - struct buffer_data_page *free_page; + struct buffer_data_read_page free_page; unsigned long nr_pages; unsigned int current_context; struct list_head *pages;
@@ -2631,7 +2631,7 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) free_buffer_page(bpage); } - free_pages((unsigned long)cpu_buffer->free_page, cpu_buffer->buffer->subbuf_order); + free_pages((unsigned long)cpu_buffer->free_page.data, cpu_buffer->free_page.order); kfree(cpu_buffer); }
@@ -6962,9 +6962,9 @@ ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu) local_irq_save(flags); arch_spin_lock(&cpu_buffer->lock); - if (cpu_buffer->free_page) { - bpage->data = cpu_buffer->free_page; - cpu_buffer->free_page = NULL; + if (cpu_buffer->free_page.data) { + *bpage = cpu_buffer->free_page; + cpu_buffer->free_page.data = NULL; } arch_spin_unlock(&cpu_buffer->lock);
@@ -7016,8 +7016,8 @@ void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, local_irq_save(flags); arch_spin_lock(&cpu_buffer->lock); - if (!cpu_buffer->free_page) { - cpu_buffer->free_page = dpage; + if (!cpu_buffer->free_page.data) { + cpu_buffer->free_page = *data_page; dpage = NULL; }
@@ -7390,7 +7390,7 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) } for_each_buffer_cpu(buffer, cpu) { - struct buffer_data_page *old_free_data_page; + struct buffer_data_read_page old_free_data_page; struct list_head old_pages; unsigned long flags;
@@ -7433,7 +7433,7 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) arch_spin_lock(&cpu_buffer->lock); old_free_data_page = cpu_buffer->free_page; - cpu_buffer->free_page = NULL; + cpu_buffer->free_page.data = NULL; arch_spin_unlock(&cpu_buffer->lock); rb_head_page_activate(cpu_buffer);
@@ -7445,7 +7445,7 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) list_del_init(&bpage->list); free_buffer_page(bpage); } - free_pages((unsigned long)old_free_data_page, old_order); + free_pages((unsigned long)old_free_data_page.data, old_free_data_page.order); rb_check_pages(cpu_buffer); }
--
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