2020-02-06 22:03:38

by Haiyang Zhang

Subject: [PATCH net] hv_netvsc: Fix XDP refcnt for synthetic and VF NICs

The caller of XDP_SETUP_PROG has already incremented refcnt in
__bpf_prog_get(), so drivers should only increment refcnt by
num_queues - 1.

To fix the issue, update netvsc_xdp_set() to add the correct number
to refcnt.

Hold a refcnt in netvsc_xdp_set()’s other caller, netvsc_attach().

And, do the same in netvsc_vf_setxdp(). Otherwise, every time when VF is
removed and added from the host side, the refcnt will be decreased by one,
which may cause page fault when unloading xdp program.

Fixes: 351e1581395f ("hv_netvsc: Add XDP support")
Signed-off-by: Haiyang Zhang <[email protected]>
---
drivers/net/hyperv/netvsc_bpf.c | 13 +++++++++++--
drivers/net/hyperv/netvsc_drv.c | 5 ++++-
2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_bpf.c b/drivers/net/hyperv/netvsc_bpf.c
index 20adfe5..b866110 100644
--- a/drivers/net/hyperv/netvsc_bpf.c
+++ b/drivers/net/hyperv/netvsc_bpf.c
@@ -120,7 +120,7 @@ int netvsc_xdp_set(struct net_device *dev, struct bpf_prog *prog,
}

if (prog)
- bpf_prog_add(prog, nvdev->num_chn);
+ bpf_prog_add(prog, nvdev->num_chn - 1);

for (i = 0; i < nvdev->num_chn; i++)
rcu_assign_pointer(nvdev->chan_table[i].bpf_prog, prog);
@@ -136,6 +136,7 @@ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct bpf_prog *prog)
{
struct netdev_bpf xdp;
bpf_op_t ndo_bpf;
+ int ret;

ASSERT_RTNL();

@@ -148,10 +149,18 @@ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct bpf_prog *prog)

memset(&xdp, 0, sizeof(xdp));

+ if (prog)
+ bpf_prog_inc(prog);
+
xdp.command = XDP_SETUP_PROG;
xdp.prog = prog;

- return ndo_bpf(vf_netdev, &xdp);
+ ret = ndo_bpf(vf_netdev, &xdp);
+
+ if (ret && prog)
+ bpf_prog_put(prog);
+
+ return ret;
}

static u32 netvsc_xdp_query(struct netvsc_device *nvdev)
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 8fc71bd..65e12cb 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -1059,9 +1059,12 @@ static int netvsc_attach(struct net_device *ndev,

prog = dev_info->bprog;
if (prog) {
+ bpf_prog_inc(prog);
ret = netvsc_xdp_set(ndev, prog, NULL, nvdev);
- if (ret)
+ if (ret) {
+ bpf_prog_put(prog);
goto err1;
+ }
}

/* In any case device is now ready */
--
1.8.3.1

2020-02-07 10:35:29

by David Miller

Subject: Re: [PATCH net] hv_netvsc: Fix XDP refcnt for synthetic and VF NICs

From: Haiyang Zhang <[email protected]>
Date: Thu, 6 Feb 2020 14:01:05 -0800

> The caller of XDP_SETUP_PROG has already incremented refcnt in
> __bpf_prog_get(), so drivers should only increment refcnt by
> num_queues - 1.
>
> To fix the issue, update netvsc_xdp_set() to add the correct number
> to refcnt.
>
> Hold a refcnt in netvsc_xdp_set()?s other caller, netvsc_attach().
>
> And, do the same in netvsc_vf_setxdp(). Otherwise, every time when VF is
> removed and added from the host side, the refcnt will be decreased by one,
> which may cause page fault when unloading xdp program.
>
> Fixes: 351e1581395f ("hv_netvsc: Add XDP support")
> Signed-off-by: Haiyang Zhang <[email protected]>

Applied, thank you.