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hv_netvsc: fix a race between netvsc_send() and netvsc_init_buf() 

Fix in commit 8809883482 ("hv_netvsc: set nvdev link after populating
chn_table") turns out to be incomplete. A crash in
netvsc_get_next_send_section() is observed on mtu change when the device
is under load. The race I identified is: if we get to netvsc_send() after
we set net_device_ctx->nvdev link in netvsc_device_add() but before we
finish netvsc_connect_vsp()->netvsc_init_buf() send_section_map is not
allocated and we crash. Unfortunately we can't set net_device_ctx->nvdev
link after the netvsc_init_buf() call as during the negotiation we need
to receive packets and on the receive path we check for it. It would
probably be possible to split nvdev into a pair of nvdev_in and nvdev_out
links and check them accordingly in get_outbound_net_device()/
get_inbound_net_device() but this looks like an overkill.

Check that send_section_map is allocated in netvsc_send().

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vitaly Kuznetsov 2016-10-19 15:53:01 +02:00 committed by David S. Miller
parent 9e58c5dc4b
commit e8f0a89cd7
1 changed files with 7 additions and 0 deletions
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7
drivers/net/hyperv/netvsc.c
View File

@ -888,6 +888,13 @@ int netvsc_send(struct hv_device *device,
if (!net_device)
return -ENODEV;
/* We may race with netvsc_connect_vsp()/netvsc_init_buf() and get
* here before the negotiation with the host is finished and
* send_section_map may not be allocated yet.
*/
if (!net_device->send_section_map)
return -EAGAIN;
out_channel = net_device->chn_table[q_idx];
packet->send_buf_index = NETVSC_INVALID_INDEX;