From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B617A39AE5 for ; Mon, 11 Dec 2023 12:23:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="G8bjNRV0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0E20C433C9; Mon, 11 Dec 2023 12:23:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702297403; bh=INgnFW8etgV5ZIh4mW5/XEKlS7hMzbp3XuZeXyAoM9o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=G8bjNRV0LvIU863tb8KVtoxG8lyDFUp8S2oo5ny5C8ybqubDzRAq4p2CbaD6ZjRKQ fZ6kC51R7INERKA1npILXWAowZEQkZr8mtF/6vERIluNWAHPd4M6PAQPFdRKIIPFgB t5Mg8tcyTEFknbZHdJig9JZWf7allB8Gqjztc3DWW+LQIekOL5CyvMpzz/kONQ5w4z MLLptuAel/uEoMsLDP09Jrw6NSzUZWnoKdT7PzD3qSpl0L8vGr6m+LIyMEZjxl8erD nv/LYQr6uCLkZFPDcRECriAYxA9kUI1MhD6tytZynbuU4FIPhoP5naRzyMLynGD0ZI lnH+J1WlZAZPw== Date: Mon, 11 Dec 2023 21:23:19 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: LKML , Linux trace kernel , Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers Subject: Re: [PATCH] ring-buffer: Fix memory leak of free page Message-Id: <20231211212319.d1a714d0139e4fd893183b9e@kernel.org> In-Reply-To: <20231210221250.7b9cc83c@rorschach.local.home> References: <20231210221250.7b9cc83c@rorschach.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sun, 10 Dec 2023 22:12:50 -0500 Steven Rostedt wrote: > From: "Steven Rostedt (Google)" > > 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. > Oops, Looks good to me. Acked-by: Masami Hiramatsu (Google) Thanks, > Cc: stable@vger.kernel.org > Fixes: 73a757e63114d ("ring-buffer: Return reader page back into existing ring buffer") > Signed-off-by: Steven Rostedt (Google) > --- > 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 a38e5a3c6803..dd37d21d6e55 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -1790,6 +1790,8 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) > free_buffer_page(bpage); > } > > + free_page((unsigned long)cpu_buffer->free_page); > + > kfree(cpu_buffer); > } > > -- > 2.42.0 > -- Masami Hiramatsu (Google)