[PATCH] virtio_net: fix virtnet_open and virtnet_probe competing for try_fill_recv

[wangyunjian <wangyunjian@huawei.com>]

In function virtnet_open() and virtnet_probe(), func try_fill_recv() will be executed at the same time. VQ in virtqueue_add() is not protected well and BUG_ON will be triggered when virito_net.ko being removed.

Test Script:
for (( i=0; i<5000000; i=i+1 )); do
	rmmod virtio_net
	modprobe virtio_net
	ifconfig eth0 up
done

[  302.336996] ------------[ cut here ]------------
[  302.338794] kernel BUG at virtio_ring.c:750!
[  302.340013] invalid opcode: 0000 [#1] SMP
[  302.340013] last sysfs file: /sys/devices/pci0000:00/0000:00:03.0/virtio0/device
[  302.340013] CPU 0
[  302.340013] Modules linked in: virtio_balloon virtio_net(-) virtio_pci virtio_ring virtio ipv6 af_packet microcode acpiphp pci_hotplug fuse loop dm_mod rtc_cmos tpm_tis rtc_core tpm i2c_piix4 rtc_lib container button floppy pcspkr tpm_bios i2c_core joydev sg usbhid hid uhci_hcd ehci_hcd usbcore edd ext3 mbcache jbd fan processor ide_pci_generic piix ide_core ata_generic at a_piix libata thermal thermal_sys hwmon sd_mod crc_t10dif kvm_ivshmem(N) scsi_mod pv_channel(N) [last unloaded: virtio]
[  302.340013] Supported: Yes
[  302.340013] Pid: 8410, comm: rmmod Tainted: GN  2.6.32.12-0.7-default #1 Standard PC (i440FX + PIIX, 1996)
[  302.340013] RIP: 0010:[<ffffffffa0323419>]  [<ffffffffa0323419>] virtqueue_detach_unused_buf+0xb9/0xc0 [virtio_ring]
[  302.340013] RSP: 0018:ffff88000c7a9e08  EFLAGS: 00010283
[  302.340013] RAX: 00000000000000f4 RBX: 0000000000000100 RCX: 0000000000004d8e
[  302.340013] RDX: ffff880001e00000 RSI: 0000000000000046 RDI: ffffffff81a71570
[  302.340013] RBP: ffff88000c987000 R08: 0000000000000000 R09: 000000000000000a
[  302.340013] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000400
[  302.340013] R13: 0000000000000000 R14: 00007fff92bc1758 R15: 0000000000000001
[  302.340013] FS:  00007f8b3995d700(0000) GS:ffff880001e00000(0000) knlGS:0000000000000000
[  302.340013] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[  302.340013] CR2: 00007fff196433e0 CR3: 000000000d07e000 CR4: 00000000000006f0
[  302.340013] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  302.340013] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[  302.340013] Process rmmod (pid: 8410, threadinfo ffff88000c7a8000, task ffff88000c7aa200)
[  302.340013] Stack:
[  302.340013]  ffff88000fbb3780 0000000000000000 ffff88000c987000 ffffffffa034b178
[  302.340013] <0> ffff88000fbb3850 ffff88000fbb3780 ffffffffa034efc0 ffff88000fbb3850
[  302.340013] <0> 0000000000000000 ffffffffa034b299 ffff88000fbb3780 ffffffffa034b406
[  302.340013] Call Trace:
[  302.340013]  [<ffffffffa034b178>] free_unused_bufs+0x88/0x120 [virtio_net]
[  302.340013]  [<ffffffffa034b299>] remove_vq_common+0x19/0x30 [virtio_net]
[  302.340013]  [<ffffffffa034b406>] virtnet_remove+0x46/0x80 [virtio_net]
[  302.340013]  [<ffffffffa0219245>] virtio_dev_remove+0x15/0x60 [virtio]
[  302.340013]  [<ffffffff81294551>] __device_release_driver+0x91/0x110
[  302.340013]  [<ffffffff81294678>] driver_detach+0xa8/0xb0
[  302.340013]  [<ffffffff81293562>] bus_remove_driver+0x82/0x110
[  302.340013]  [<ffffffff8107aea4>] sys_delete_module+0x1c4/0x290
[  302.340013]  [<ffffffff81002f7b>] system_call_fastpath+0x16/0x1b
[  302.340013]  [<00007f8b394c7de7>] 0x7f8b394c7de7
[  302.340013] Code: c3 01 49 83 c4 04 e8 30 10 07 e1 8b 55 38 39 da 77 d0 8b 75 2c 31 c0 48 c7 c7 ba 4b 32 a0 e8 18 10 07 e1 8b 45 2c 3b 45 38 74 82 <0f> 0b eb fe 0f 1f 00 48 83 ec 28 48 89 6c 24 08 48 89 1c 24 48
[  302.340013] RIP  [<ffffffffa0323419>] virtqueue_detach_unused_buf+0xb9/0xc0 [virtio_ring]
[  302.340013]  RSP <ffff88000c7a9e08>
[  302.438579] ---[ end trace 1e583bdb5b2644f1 ]---


Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
---
 drivers/net/virtio_net.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 49d84e5..4528ef8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -818,10 +818,6 @@ static int virtnet_open(struct net_device *dev)
        int i;

        for (i = 0; i < vi->max_queue_pairs; i++) {
-               if (i < vi->curr_queue_pairs)
-                       /* Make sure we have some buffers: if oom use wq. */
-                       if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
-                               schedule_delayed_work(&vi->refill, 0);
                virtnet_napi_enable(&vi->rq[i]);
        }