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Date: Wed, 2 Feb 2022 17:05:20 +0000
From: "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To: Tianyu Lan <ltykernel@...il.com>,
KY Srinivasan <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
Dexuan Cui <decui@...rosoft.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
"davem@...emloft.net" <davem@...emloft.net>,
"kuba@...nel.org" <kuba@...nel.org>,
"hch@...radead.org" <hch@...radead.org>,
"m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
"robin.murphy@....com" <robin.murphy@....com>
CC: Tianyu Lan <Tianyu.Lan@...rosoft.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] Netvsc: Call hv_unmap_memory() in the
netvsc_device_remove()
From: Tianyu Lan <ltykernel@...il.com> Sent: Tuesday, February 1, 2022 8:32 AM
>
> netvsc_device_remove() calls vunmap() inside which should not be
> called in the interrupt context. Current code calls hv_unmap_memory()
> in the free_netvsc_device() which is rcu callback and maybe called
> in the interrupt context. This will trigger BUG_ON(in_interrupt())
> in the vunmap(). Fix it via moving hv_unmap_memory() to netvsc_device_
> remove().
I think this change can fail to call hv_unmap_memory() in an error case.
If netvsc_init_buf() fails after hv_map_memory() succeeds for the receive
buffer or for the send buffer, no corresponding hv_unmap_memory() will
be done. The failure in netvsc_init_buf() will cause netvsc_connect_vsp()
to fail, so netvsc_add_device() will "goto close" where free_netvsc_device()
will be called. But free_netvsc_device() no longer calls hv_unmap_memory(),
so it won't ever happen. netvsc_device_remove() is never called in this case
because netvsc_add_device() failed.
Michael
>
> Fixes: 846da38de0e8 ("net: netvsc: Add Isolation VM support for netvsc driver")
> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> ---
> drivers/net/hyperv/netvsc.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index afa81a9480cc..f989f920d4ce 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -154,19 +154,15 @@ static void free_netvsc_device(struct rcu_head *head)
>
> kfree(nvdev->extension);
>
> - if (nvdev->recv_original_buf) {
> - hv_unmap_memory(nvdev->recv_buf);
> + if (nvdev->recv_original_buf)
> vfree(nvdev->recv_original_buf);
> - } else {
> + else
> vfree(nvdev->recv_buf);
> - }
>
> - if (nvdev->send_original_buf) {
> - hv_unmap_memory(nvdev->send_buf);
> + if (nvdev->send_original_buf)
> vfree(nvdev->send_original_buf);
> - } else {
> + else
> vfree(nvdev->send_buf);
> - }
>
> bitmap_free(nvdev->send_section_map);
>
> @@ -765,6 +761,12 @@ void netvsc_device_remove(struct hv_device *device)
> netvsc_teardown_send_gpadl(device, net_device, ndev);
> }
>
> + if (net_device->recv_original_buf)
> + hv_unmap_memory(net_device->recv_buf);
> +
> + if (net_device->send_original_buf)
> + hv_unmap_memory(net_device->send_buf);
> +
> /* Release all resources */
> free_netvsc_device_rcu(net_device);
> }
> --
> 2.25.1
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