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Tue, 18 Feb 2025 20:54:56 -0800 (PST) Date: Tue, 18 Feb 2025 20:54:55 -0800 From: Stanislav Fomichev To: Jakub Kicinski Cc: Stanislav Fomichev , netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, Saeed Mahameed Subject: Re: [PATCH net-next v4 07/12] net: hold netdev instance lock during ndo_bpf Message-ID: References: <20250218020948.160643-1-sdf@fomichev.me> <20250218020948.160643-8-sdf@fomichev.me> <20250218190258.5c82026b@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250218190258.5c82026b@kernel.org> On 02/18, Jakub Kicinski wrote: > On Mon, 17 Feb 2025 18:09:43 -0800 Stanislav Fomichev wrote: > > --- a/kernel/bpf/offload.c > > +++ b/kernel/bpf/offload.c > > @@ -528,10 +528,10 @@ struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr) > > return ERR_PTR(-ENOMEM); > > > > bpf_map_init_from_attr(&offmap->map, attr); > > - > > rtnl_lock(); > > - down_write(&bpf_devs_lock); > > offmap->netdev = __dev_get_by_index(net, attr->map_ifindex); > > + netdev_lock_ops(offmap->netdev); > > + down_write(&bpf_devs_lock); > > err = bpf_dev_offload_check(offmap->netdev); > > if (err) > > goto err_unlock; > > @@ -548,12 +548,14 @@ struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr) > > > > list_add_tail(&offmap->offloads, &ondev->maps); > > up_write(&bpf_devs_lock); > > + netdev_unlock_ops(offmap->netdev); > > rtnl_unlock(); > > > > return &offmap->map; > > > > err_unlock: > > up_write(&bpf_devs_lock); > > + netdev_unlock_ops(offmap->netdev); > > rtnl_unlock(); > > bpf_map_area_free(offmap); > > return ERR_PTR(err); > > Any reason for this lock ordering? My intuition would be from biggest > to smallest, so rtnl_lock -> sem -> instance >From rtnl we take the following: rtnl_newlink rtnl_lock do_setlink netdev_lock_ops dev_change_xdp_fd dev_xdp_attach bpf_offload_dev_match down_read(bpf_devs_lock) So I made bpf syscall path to look similar: map_create bpf_map_offload_map_alloc rtnl_lock netdev_ops_lock down_write(bpf_devs_lock)