* [0/1 bpf-next] fix panic bringing up veth with xdp progs
@ 2022-11-08 22:16 John Fastabend
2022-11-08 22:16 ` [1/1 bpf-next] bpf: veth driver panics when xdp prog attached before veth_open John Fastabend
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: John Fastabend @ 2022-11-08 22:16 UTC (permalink / raw)
To: daniel, kuba, davem, ast; +Cc: netdev, bpf, john.fastabend
Not sure if folks want to take this through BPF tree or networking tree.
I took a quick look and didn't see any pending fixes so seems no one
has noticed the panic yet. It reproducible and easy to repro.
I put bpf in the title thinking it woudl be great to run through the
BPF selftests given its XDP triggering the panic.
Sorry maintainers resent with CC'ing actual lists. Had a scripting
issue. Also dropped henqqi has they are bouncing.
Thanks!
John Fastabend (1):
bpf: veth driver panics when xdp prog attached before veth_open
drivers/net/veth.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--
2.33.0
^ permalink raw reply [flat|nested] 4+ messages in thread
* [1/1 bpf-next] bpf: veth driver panics when xdp prog attached before veth_open
2022-11-08 22:16 [0/1 bpf-next] fix panic bringing up veth with xdp progs John Fastabend
@ 2022-11-08 22:16 ` John Fastabend
2022-11-10 2:25 ` [0/1 bpf-next] fix panic bringing up veth with xdp progs Jakub Kicinski
2022-11-10 5:10 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: John Fastabend @ 2022-11-08 22:16 UTC (permalink / raw)
To: daniel, kuba, davem, ast; +Cc: netdev, bpf, john.fastabend
The following panic is observed when bringing up (veth_open) a veth device
that has an XDP program attached.
[ 61.519185] kernel BUG at net/core/dev.c:6442!
[ 61.519456] invalid opcode: 0000 [#1] PREEMPT SMP PTI
[ 61.519752] CPU: 0 PID: 408 Comm: ip Tainted: G W 6.1.0-rc2-185930-gd9095f92950b-dirty #26
[ 61.520288] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
[ 61.520806] RIP: 0010:napi_enable+0x3d/0x40
[ 61.521077] Code: f6 f6 80 61 08 00 00 02 74 0d 48 83 bf 88 01 00 00 00 74 03 80 cd 01 48 89 d0 f0 48 0f b1 4f 10 48 39 c2 75 c8 c3 cc cc cc cc <0f> 0b 90 48 8b 87 b0 00 00 00 48 81 c7 b0 00 00 00 45 31 c0 48 39
[ 61.522226] RSP: 0018:ffffbc9800cc36f8 EFLAGS: 00010246
[ 61.522557] RAX: 0000000000000001 RBX: 0000000000000300 RCX: 0000000000000001
[ 61.523004] RDX: 0000000000000010 RSI: ffffffff8b0de852 RDI: ffff9f03848e5000
[ 61.523452] RBP: 0000000000000000 R08: 0000000000000800 R09: 0000000000000000
[ 61.523899] R10: ffff9f0384a96800 R11: ffffffffffa48061 R12: ffff9f03849c3000
[ 61.524345] R13: 0000000000000300 R14: ffff9f03848e5000 R15: 0000001000000100
[ 61.524792] FS: 00007f58cb64d2c0(0000) GS:ffff9f03bbc00000(0000) knlGS:0000000000000000
[ 61.525301] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 61.525673] CR2: 00007f6cc629b498 CR3: 000000010498c000 CR4: 00000000000006f0
[ 61.526121] Call Trace:
[ 61.526284] <TASK>
[ 61.526425] __veth_napi_enable_range+0xd6/0x230
[ 61.526723] veth_enable_xdp+0xd0/0x160
[ 61.526969] veth_open+0x2e/0xc0
[ 61.527180] __dev_open+0xe2/0x1b0
[ 61.527405] __dev_change_flags+0x1a1/0x210
[ 61.527673] dev_change_flags+0x1c/0x60
This happens because we are calling veth_napi_enable() on already enabled
queues. The root cause is in commit 2e0de6366ac16 changed the control logic
dropping this case,
if (priv->_xdp_prog) {
err = veth_enable_xdp(dev);
if (err)
return err;
- } else if (veth_gro_requested(dev)) {
+ /* refer to the logic in veth_xdp_set() */
+ if (!rtnl_dereference(peer_rq->napi)) {
+ err = veth_napi_enable(peer);
+ if (err)
+ return err;
+ }
so that now veth_napi_enable is called if the peer has not yet
initialiazed its peer_rq->napi. The issue is this will happen
even if the NIC is not up. Then in veth_enable_xdp just above
we have similar path,
veth_enable_xdp
napi_already_on = (dev->flags & IFF_UP) && rcu_access_pointer(rq->napi)
err = veth_enable_xdp_range(dev, 0, dev->real_num_rx_queues, napi_already_on);
The trouble is an xdp prog is assigned before bringing the device up each
of the veth_open path will enable the peers xdp napi structs. But then when
we bring the peer up it will similar try to enable again because from
veth_open the IFF_UP flag is not set until after the op in __dev_open so
we believe napi_alread_on = false.
To fix this just drop the IFF_UP test and rely on checking if the napi
struct is enabled. This also matches the peer check in veth_xdp for
disabling.
To reproduce run ./test_xdp_meta.sh I found adding Cilium/Tetragon tests
for XDP.
Fixes: 2e0de6366ac16 ("veth: Avoid drop packets when xdp_redirect performs")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
drivers/net/veth.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index b1ed5a93b6c5..2a4592780141 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -1125,7 +1125,7 @@ static int veth_enable_xdp(struct net_device *dev)
int err, i;
rq = &priv->rq[0];
- napi_already_on = (dev->flags & IFF_UP) && rcu_access_pointer(rq->napi);
+ napi_already_on = rcu_access_pointer(rq->napi);
if (!xdp_rxq_info_is_reg(&priv->rq[0].xdp_rxq)) {
err = veth_enable_xdp_range(dev, 0, dev->real_num_rx_queues, napi_already_on);
--
2.33.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [0/1 bpf-next] fix panic bringing up veth with xdp progs
2022-11-08 22:16 [0/1 bpf-next] fix panic bringing up veth with xdp progs John Fastabend
2022-11-08 22:16 ` [1/1 bpf-next] bpf: veth driver panics when xdp prog attached before veth_open John Fastabend
@ 2022-11-10 2:25 ` Jakub Kicinski
2022-11-10 5:10 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Jakub Kicinski @ 2022-11-10 2:25 UTC (permalink / raw)
To: John Fastabend; +Cc: daniel, davem, ast, netdev, bpf, Paolo Abeni
On Tue, 8 Nov 2022 14:16:49 -0800 John Fastabend wrote:
> Not sure if folks want to take this through BPF tree or networking tree.
Whatever's easiest :) FWIW
Acked-by: Jakub Kicinski <kuba@kernel.org>
> I took a quick look and didn't see any pending fixes so seems no one
> has noticed the panic yet. It reproducible and easy to repro.
>
> I put bpf in the title thinking it woudl be great to run through the
> BPF selftests given its XDP triggering the panic.
>
> Sorry maintainers resent with CC'ing actual lists. Had a scripting
> issue. Also dropped henqqi has they are bouncing.
Adding Paolo, who had comments on this patch in the past.
The entire concept is worth mainintaining in your opinion, I take it?
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [0/1 bpf-next] fix panic bringing up veth with xdp progs
2022-11-08 22:16 [0/1 bpf-next] fix panic bringing up veth with xdp progs John Fastabend
2022-11-08 22:16 ` [1/1 bpf-next] bpf: veth driver panics when xdp prog attached before veth_open John Fastabend
2022-11-10 2:25 ` [0/1 bpf-next] fix panic bringing up veth with xdp progs Jakub Kicinski
@ 2022-11-10 5:10 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2022-11-10 5:10 UTC (permalink / raw)
To: John Fastabend; +Cc: daniel, kuba, davem, ast, netdev, bpf
Hello:
This patch was applied to bpf/bpf-next.git (master)
by Martin KaFai Lau <martin.lau@kernel.org>:
On Tue, 8 Nov 2022 14:16:49 -0800 you wrote:
> Not sure if folks want to take this through BPF tree or networking tree.
> I took a quick look and didn't see any pending fixes so seems no one
> has noticed the panic yet. It reproducible and easy to repro.
>
> I put bpf in the title thinking it woudl be great to run through the
> BPF selftests given its XDP triggering the panic.
>
> [...]
Here is the summary with links:
- [1/1,bpf-next] bpf: veth driver panics when xdp prog attached before veth_open
https://git.kernel.org/bpf/bpf-next/c/5e5dc33d5dac
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 4+ messages in thread
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-- links below jump to the message on this page --
2022-11-08 22:16 [0/1 bpf-next] fix panic bringing up veth with xdp progs John Fastabend
2022-11-08 22:16 ` [1/1 bpf-next] bpf: veth driver panics when xdp prog attached before veth_open John Fastabend
2022-11-10 2:25 ` [0/1 bpf-next] fix panic bringing up veth with xdp progs Jakub Kicinski
2022-11-10 5:10 ` patchwork-bot+netdevbpf
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