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McKenney" To: "Joel Fernandes (Google)" Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [RFC 1/5] net: rtnetlink: Fix incorrect RCU API usage Reply-To: paulmck@linux.ibm.com References: <20190220040827.136184-1-joel@joelfernandes.org> <20190220040827.136184-2-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190220040827.136184-2-joel@joelfernandes.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19022016-0068-0000-0000-00000396CCD5 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010632; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000281; SDB=6.01163853; UDB=6.00607726; IPR=6.00944437; MB=3.00025669; MTD=3.00000008; XFM=3.00000015; UTC=2019-02-20 16:40:37 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022016-0069-0000-0000-000047924703 Message-Id: <20190220164034.GM11787@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-20_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902200117 Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Tue, Feb 19, 2019 at 11:08:23PM -0500, Joel Fernandes (Google) wrote: > From: Joel Fernandes > > 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] * > > Signed-off-by: Joel Fernandes First, thank you for doing this! I was going to complain that these were update-side accesses, but it looks like rtnl_dereference() already handles both readers and updaters. So looks good to me, but the maintainers of course have the final word. Thanx, Paul > --- > 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 >