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Message-ID: <ZH3zUdkxvxgaYjxf@kernel.org>
Date: Mon, 5 Jun 2023 16:38:09 +0200
From: Simon Horman <horms@...nel.org>
To: Eelco Chaudron <echaudro@...hat.com>
Cc: Simon Horman <simon.horman@...igine.com>, dev@...nvswitch.org,
netdev@...r.kernel.org, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, davem@...emloft.net
Subject: Re: [ovs-dev] [PATCH net] net: openvswitch: fix upcall counter
access before allocation
On Mon, Jun 05, 2023 at 03:53:59PM +0200, Eelco Chaudron wrote:
>
>
> On 5 Jun 2023, at 15:07, Simon Horman wrote:
>
> > On Mon, Jun 05, 2023 at 02:54:35PM +0200, Eelco Chaudron wrote:
> >>
> >>
> >> On 5 Jun 2023, at 14:41, Simon Horman wrote:
> >>
> >>> On Mon, Jun 05, 2023 at 10:59:50AM +0200, Eelco Chaudron wrote:
> >>>> Currently, the per cpu upcall counters are allocated after the vport is
> >>>> created and inserted into the system. This could lead to the datapath
> >>>> accessing the counters before they are allocated resulting in a kernel
> >>>> Oops.
> >>>>
> >>>> Here is an example:
> >>>>
> >>>> PID: 59693 TASK: ffff0005f4f51500 CPU: 0 COMMAND: "ovs-vswitchd"
> >>>> #0 [ffff80000a39b5b0] __switch_to at ffffb70f0629f2f4
> >>>> #1 [ffff80000a39b5d0] __schedule at ffffb70f0629f5cc
> >>>> #2 [ffff80000a39b650] preempt_schedule_common at ffffb70f0629fa60
> >>>> #3 [ffff80000a39b670] dynamic_might_resched at ffffb70f0629fb58
> >>>> #4 [ffff80000a39b680] mutex_lock_killable at ffffb70f062a1388
> >>>> #5 [ffff80000a39b6a0] pcpu_alloc at ffffb70f0594460c
> >>>> #6 [ffff80000a39b750] __alloc_percpu_gfp at ffffb70f05944e68
> >>>> #7 [ffff80000a39b760] ovs_vport_cmd_new at ffffb70ee6961b90 [openvswitch]
> >>>> ...
> >>>>
> >>>> PID: 58682 TASK: ffff0005b2f0bf00 CPU: 0 COMMAND: "kworker/0:3"
> >>>> #0 [ffff80000a5d2f40] machine_kexec at ffffb70f056a0758
> >>>> #1 [ffff80000a5d2f70] __crash_kexec at ffffb70f057e2994
> >>>> #2 [ffff80000a5d3100] crash_kexec at ffffb70f057e2ad8
> >>>> #3 [ffff80000a5d3120] die at ffffb70f0628234c
> >>>> #4 [ffff80000a5d31e0] die_kernel_fault at ffffb70f062828a8
> >>>> #5 [ffff80000a5d3210] __do_kernel_fault at ffffb70f056a31f4
> >>>> #6 [ffff80000a5d3240] do_bad_area at ffffb70f056a32a4
> >>>> #7 [ffff80000a5d3260] do_translation_fault at ffffb70f062a9710
> >>>> #8 [ffff80000a5d3270] do_mem_abort at ffffb70f056a2f74
> >>>> #9 [ffff80000a5d32a0] el1_abort at ffffb70f06297dac
> >>>> #10 [ffff80000a5d32d0] el1h_64_sync_handler at ffffb70f06299b24
> >>>> #11 [ffff80000a5d3410] el1h_64_sync at ffffb70f056812dc
> >>>> #12 [ffff80000a5d3430] ovs_dp_upcall at ffffb70ee6963c84 [openvswitch]
> >>>> #13 [ffff80000a5d3470] ovs_dp_process_packet at ffffb70ee6963fdc [openvswitch]
> >>>> #14 [ffff80000a5d34f0] ovs_vport_receive at ffffb70ee6972c78 [openvswitch]
> >>>> #15 [ffff80000a5d36f0] netdev_port_receive at ffffb70ee6973948 [openvswitch]
> >>>> #16 [ffff80000a5d3720] netdev_frame_hook at ffffb70ee6973a28 [openvswitch]
> >>>> #17 [ffff80000a5d3730] __netif_receive_skb_core.constprop.0 at ffffb70f06079f90
> >>>>
> >>>> We moved the per cpu upcall counter allocation to the existing vport
> >>>> alloc and free functions to solve this.
> >>>>
> >>>> Fixes: 95637d91fefd ("net: openvswitch: release vport resources on failure")
> >>>> Fixes: 1933ea365aa7 ("net: openvswitch: Add support to count upcall packets")
> >>>> Signed-off-by: Eelco Chaudron <echaudro@...hat.com>
> >>>> ---
> >>>> net/openvswitch/datapath.c | 19 -------------------
> >>>> net/openvswitch/vport.c | 8 ++++++++
> >>>> 2 files changed, 8 insertions(+), 19 deletions(-)
> >>>>
> >>>> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> >>>> index fcee6012293b..58f530f60172 100644
> >>>> --- a/net/openvswitch/datapath.c
> >>>> +++ b/net/openvswitch/datapath.c
> >>>> @@ -236,9 +236,6 @@ void ovs_dp_detach_port(struct vport *p)
> >>>> /* First drop references to device. */
> >>>> hlist_del_rcu(&p->dp_hash_node);
> >>>>
> >>>> - /* Free percpu memory */
> >>>> - free_percpu(p->upcall_stats);
> >>>> -
> >>>> /* Then destroy it. */
> >>>> ovs_vport_del(p);
> >>>> }
> >>>> @@ -1858,12 +1855,6 @@ static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
> >>>> goto err_destroy_portids;
> >>>> }
> >>>>
> >>>> - vport->upcall_stats = netdev_alloc_pcpu_stats(struct vport_upcall_stats_percpu);
> >>>> - if (!vport->upcall_stats) {
> >>>> - err = -ENOMEM;
> >>>> - goto err_destroy_vport;
> >>>> - }
> >>>> -
> >>>> err = ovs_dp_cmd_fill_info(dp, reply, info->snd_portid,
> >>>> info->snd_seq, 0, OVS_DP_CMD_NEW);
> >>>> BUG_ON(err < 0);
> >>>> @@ -1876,8 +1867,6 @@ static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
> >>>> ovs_notify(&dp_datapath_genl_family, reply, info);
> >>>> return 0;
> >>>>
> >>>> -err_destroy_vport:
> >>>> - ovs_dp_detach_port(vport);
> >>>> err_destroy_portids:
> >>>> kfree(rcu_dereference_raw(dp->upcall_portids));
> >>>> err_unlock_and_destroy_meters:
> >>>> @@ -2322,12 +2311,6 @@ static int ovs_vport_cmd_new(struct sk_buff *skb, struct genl_info *info)
> >>>> goto exit_unlock_free;
> >>>> }
> >>>>
> >>>> - vport->upcall_stats = netdev_alloc_pcpu_stats(struct vport_upcall_stats_percpu);
> >>>> - if (!vport->upcall_stats) {
> >>>> - err = -ENOMEM;
> >>>> - goto exit_unlock_free_vport;
> >>>> - }
> >>>> -
> >>>> err = ovs_vport_cmd_fill_info(vport, reply, genl_info_net(info),
> >>>> info->snd_portid, info->snd_seq, 0,
> >>>> OVS_VPORT_CMD_NEW, GFP_KERNEL);
> >>>> @@ -2345,8 +2328,6 @@ static int ovs_vport_cmd_new(struct sk_buff *skb, struct genl_info *info)
> >>>> ovs_notify(&dp_vport_genl_family, reply, info);
> >>>> return 0;
> >>>>
> >>>> -exit_unlock_free_vport:
> >>>> - ovs_dp_detach_port(vport);
> >>>> exit_unlock_free:
> >>>> ovs_unlock();
> >>>> kfree_skb(reply);
> >>>> diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
> >>>> index 7e0f5c45b512..e91ae5dd7d22 100644
> >>>> --- a/net/openvswitch/vport.c
> >>>> +++ b/net/openvswitch/vport.c
> >>>
> >>> Hi Eelco,
> >>>
> >>> could we move to a more idiomatic implementation
> >>> of the error path in ovs_vport_alloc() ?
> >>>
> >>> I know it's not strictly related to this change, but OTOH, it is.
> >>
> >> Thanks Simon for the review…
> >>
> >> I decided to stick to fixing the issue, not trying to do cleanup stuff while at it :) But if there are no further comments by tomorrow, I can send a v2 including this change.
> >
> > Yeah, I see that. And I might have done the same thing.
> > But, OTOH, this change is making the error path more complex
> > (or at least more prone to error).
> >
> > In any case, the fix looks good.
>
> Thanks, just to clarify if we get no further feedback on this patch, do you prefer a v2 with the error path changes?
Thanks Eelco,
Yes, that is my preference.
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