4.19-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (Google) rostedt@goodmis.org
commit 17d801758157bec93f26faaf5ff1a8b9a552d67a upstream.
Reading the ring buffer does a swap of a sub-buffer within the ring buffer with a empty sub-buffer. This allows the reader to have full access to the content of the sub-buffer that was swapped out without having to worry about contention with the writer.
The readers call ring_buffer_alloc_read_page() to allocate a page that will be used to swap with the ring buffer. When the code is finished with the reader page, it calls ring_buffer_free_read_page(). Instead of freeing the page, it stores it as a spare. Then next call to ring_buffer_alloc_read_page() will return this spare instead of calling into the memory management system to allocate a new page.
Unfortunately, on freeing of the ring buffer, this spare page is not freed, and causes a memory leak.
Link: https://lore.kernel.org/linux-trace-kernel/20231210221250.7b9cc83c@rorschach...
Cc: stable@vger.kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Fixes: 73a757e63114d ("ring-buffer: Return reader page back into existing ring buffer") Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/ring_buffer.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1344,6 +1344,8 @@ static void rb_free_cpu_buffer(struct ri free_buffer_page(bpage); }
+ free_page((unsigned long)cpu_buffer->free_page); + kfree(cpu_buffer); }