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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: "K. Y. Srinivasan" <kys@microsoft.com>, devel@linuxdriverproject.org
Cc: Haiyang Zhang <haiyangz@microsoft.com>,
	linux-kernel@vger.kernel.org, Dexuan Cui <decui@microsoft.com>,
	Jason Wang <jasowang@redhat.com>
Subject: [PATCH 4/4] hyperv: netvsc: improve protection against rescind offer
Date: Tue,  3 Feb 2015 18:00:39 +0100	[thread overview]
Message-ID: <1422982839-3948-5-git-send-email-vkuznets@redhat.com> (raw)
In-Reply-To: <1422982839-3948-1-git-send-email-vkuznets@redhat.com>

The check added in commit c3582a2c4d0b ("hyperv: Add support for vNIC hot
removal") is incomplete as there is no synchronization between
vmbus_onoffer_rescind() and netvsc_send(). In case we get the offer after we
checked out_channel->rescind and before netvsc_send() finishes its job we can
get a crash as we'll be dealing with already freed channel.

Make netvsc_send() take additional reference to the channel with newly
introduced vmbus_get_channel(), this guarantees we won't lose the channel. We
can still get rescind while we're processing but this won't cause a crash.

Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/net/hyperv/netvsc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 9f49c01..d9b13a1 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -763,11 +763,16 @@ int netvsc_send(struct hv_device *device,
 	out_channel = net_device->chn_table[packet->q_idx];
 	if (out_channel == NULL)
 		out_channel = device->channel;
-	packet->channel = out_channel;
+	packet->channel = vmbus_get_channel(out_channel);
 
-	if (out_channel->rescind)
+	if (!packet->channel)
 		return -ENODEV;
 
+	if (out_channel->rescind) {
+		vmbus_put_channel(out_channel);
+		return -ENODEV;
+	}
+
 	if (packet->page_buf_cnt) {
 		ret = vmbus_sendpacket_pagebuffer(out_channel,
 						  packet->page_buf,
@@ -810,6 +815,7 @@ int netvsc_send(struct hv_device *device,
 			   packet, ret);
 	}
 
+	vmbus_put_channel(packet->channel);
 	return ret;
 }
 
-- 
1.9.3


  parent reply	other threads:[~2015-02-03 17:00 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-03 17:00 [PATCH 0/4] Drivers: hv: Further protection for the rescind path Vitaly Kuznetsov
2015-02-03 17:00 ` [PATCH 1/4] Drivers: hv: vmbus: implement get/put usage workflow for vmbus channels Vitaly Kuznetsov
2015-02-04  8:18   ` Dexuan Cui
2015-02-04  9:32     ` Vitaly Kuznetsov
2015-02-04  9:54       ` Dexuan Cui
2015-02-04  9:14   ` Jason Wang
2015-02-04  9:33     ` Vitaly Kuznetsov
2015-02-03 17:00 ` [PATCH 2/4] Drivers: hv: vmbus: do not lose rescind offer on failure in vmbus_process_offer() Vitaly Kuznetsov
2015-02-04  7:42   ` Dexuan Cui
2015-02-03 17:00 ` [PATCH 3/4] Drivers: hv: vmbus: protect vmbus_get_outgoing_channel() against channel removal Vitaly Kuznetsov
2015-02-04  7:27   ` Dexuan Cui
2015-02-03 17:00 ` Vitaly Kuznetsov [this message]
2015-02-04  7:29   ` [PATCH 4/4] hyperv: netvsc: improve protection against rescind offer Dexuan Cui
2015-02-04 18:26 ` [PATCH 0/4] Drivers: hv: Further protection for the rescind path KY Srinivasan
2015-02-05 10:10   ` Vitaly Kuznetsov
2015-02-05 12:44     ` Dexuan Cui
2015-02-05 22:47       ` KY Srinivasan
2015-02-06 14:53         ` Dexuan Cui
2015-02-07 16:27           ` KY Srinivasan
2015-02-05 15:52     ` KY Srinivasan

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