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Message-Id: <20190225210551.GV4072@linux.ibm.com>
Date: Mon, 25 Feb 2019 13:05:51 -0800
From: "Paul E. McKenney" <paulmck@...ux.ibm.com>
To: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: linux-kernel@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
Christian Brauner <christian@...uner.io>,
Daniel Borkmann <daniel@...earbox.net>,
David Ahern <dsahern@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Ingo Molnar <mingo@...hat.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Josh Triplett <josh@...htriplett.org>, keescook@...omium.org,
kernel-hardening@...ts.openwall.com, kernel-team@...roid.com,
Kirill Tkhai <ktkhai@...tuozzo.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Martin KaFai Lau <kafai@...com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
netdev@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
Quentin Perret <quentin.perret@....com>, rcu@...r.kernel.org,
Song Liu <songliubraving@...com>, Steven Rostedt <rostedt@...dmis.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
xdp-newbies@...r.kernel.org, Yonghong Song <yhs@...com>
Subject: Re: [PATCH v2 1/6] net: rtnetlink: Fix incorrect RCU API usage
On Sat, Feb 23, 2019 at 01:34:29AM -0500, Joel Fernandes (Google) wrote:
> rtnl_register_internal() and rtnl_unregister_all tries to directly
> dereference an RCU protected pointed outside RCU read side section.
> While this is Ok to do since a lock is held, let us use the correct
> API to avoid programmer bugs in the future.
>
> This also fixes sparse warnings arising from not using RCU API.
>
> net/core/rtnetlink.c:332:13: warning: incorrect type in assignment
> (different address spaces) net/core/rtnetlink.c:332:13: expected
> struct rtnl_link **tab net/core/rtnetlink.c:332:13: got struct
> rtnl_link *[noderef] <asn:4>*<noident>
>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
>From an RCU perspective:
Reviewed-by: Paul E. McKenney <paulmck@...ux.ibm.com>
> ---
> net/core/rtnetlink.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 5ea1bed08ede..98be4b4818a9 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -188,7 +188,7 @@ static int rtnl_register_internal(struct module *owner,
> msgindex = rtm_msgindex(msgtype);
>
> rtnl_lock();
> - tab = rtnl_msg_handlers[protocol];
> + tab = rtnl_dereference(rtnl_msg_handlers[protocol]);
> if (tab == NULL) {
> tab = kcalloc(RTM_NR_MSGTYPES, sizeof(void *), GFP_KERNEL);
> if (!tab)
> @@ -329,7 +329,7 @@ void rtnl_unregister_all(int protocol)
> BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX);
>
> rtnl_lock();
> - tab = rtnl_msg_handlers[protocol];
> + tab = rtnl_dereference(rtnl_msg_handlers[protocol]);
> if (!tab) {
> rtnl_unlock();
> return;
> --
> 2.21.0.rc0.258.g878e2cd30e-goog
>
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