> -----Original Message----- > From: Gaëtan Rivet [mailto:gr...@u256.net] > Sent: Thursday, February 17, 2022 1:29 AM > To: wangyunjian <wangyunj...@huawei.com>; <d...@openvswitch.org> > <d...@openvswitch.org>; Ilya Maximets <i.maxim...@ovn.org> > Cc: amore...@redhat.com; dingxiaoxiong <dingxiaoxi...@huawei.com>; 贺鹏 > <xnhp0...@gmail.com> > Subject: Re: [ovs-dev] [PATCH] ofproto: fix use-after-free for "ofproto". > > On Wed, Feb 16, 2022, at 14:24, wangyunjian wrote: > >> -----Original Message----- > >> From: Gaëtan Rivet [mailto:gr...@u256.net] > >> Sent: Wednesday, February 16, 2022 7:34 PM > >> To: wangyunjian <wangyunj...@huawei.com>; <d...@openvswitch.org> > >> <d...@openvswitch.org>; Ilya Maximets <i.maxim...@ovn.org> > >> Cc: dingxiaoxiong <dingxiaoxi...@huawei.com> > >> Subject: Re: [ovs-dev] [PATCH] ofproto: fix use-after-free for "ofproto". > >> > >> On Fri, Dec 3, 2021, at 12:25, Yunjian Wang via dev wrote: > >> > When handler threads lookup a "ofproto" and use it, main thread > >> > maybe remove and free the "ofproto" at the same time. The "ofproto" > >> > has not been protected well, which can lead to an OVS crash. > >> > > >> > This patch fixes this by making the "ofproto" lookup RCU-safe by > >> > using cmap instead of hmap and moving remove "ofproto" call before > >> > xlate_txn_commit(). > >> > > >> > >> I don't understand the point of moving the cmap_remove() call before > >> xlate_txn_commit(). > > > > To use of the rcu_synchronize in the xlate_txn_commit to avoid access > > to the ofproto from other thread through uuid map. > > > > Yes the reason is clear. > > But my question is why is it needed? It seems that the ofproto lifecycle was > written with the assumption that it would still be used while being destroyed. > > Can you explain why it needs to be changed?
I didn't describe the problem clearly before. The main problem is that hmap variable is not thread safe. The all_ofproto_dpifs_by_uuid variable uses the hmap structure, which maybe be accessed by main thread and handler threads. Thanks, Yunjian > > -- > Gaetan Rivet _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
