Re: [dpdk-dev] [dpdk-stable] [DPDK] net/virtio: fix check scatter on all Rx queues

[Kevin Traynor <ktraynor@redhat.com>]

On 15/09/2021 19:37, David Marchand wrote:
> On Wed, Aug 4, 2021 at 10:36 AM <zhihongx.peng@intel.com> wrote:
>>
>> From: Zhihong Peng <zhihongx.peng@intel.com>
>>
>> This patch fixes the wrong way to obtain virtqueue.
>> The end of virtqueue cannot be judged based on whether
>> the array is NULL.
> 
> Indeed, good catch.
> 
> I can reproduce a crash with v20.11.3 which has backport of 4e8169eb0d2d.
> I can not see it with main: maybe due to a lucky allocation or size
> requested to rte_zmalloc... ?
> 
> The usecase is simple, I am surprised no validation caught it.
> 
> # gdb ./build/app/dpdk-testpmd -ex 'run --vdev
> net_virtio_user0,path=/dev/vhost-net,iface=titi,queues=3 -a 0:0:0.0 --
> -i'
> 
> ...
> 
> Thread 1 "dpdk-testpmd" received signal SIGSEGV, Segmentation fault.
> virtio_rx_mem_pool_buf_size (mp=0x110429983) at
> ../drivers/net/virtio/virtio_ethdev.c:873
> 873        return rte_pktmbuf_data_room_size(mp) - RTE_PKTMBUF_HEADROOM;
> Missing separate debuginfos, use: yum debuginfo-install
> elfutils-libelf-0.182-3.el8.x86_64 libbpf-0.2.0-1.el8.x86_64
> (gdb) bt
> #0  virtio_rx_mem_pool_buf_size (mp=0x110429983) at
> ../drivers/net/virtio/virtio_ethdev.c:873
> #1  0x0000000000e370d1 in virtio_check_scatter_on_all_rx_queues
> (frame_size=1530, dev=0x1799a40 <rte_eth_devices>) at
> ../drivers/net/virtio/virtio_ethdev.c:907
> #2  virtio_mtu_set (dev=0x1799a40 <rte_eth_devices>, mtu=<optimized
> out>) at ../drivers/net/virtio/virtio_ethdev.c:938
> #3  0x00000000008c30e5 in rte_eth_dev_set_mtu
> (port_id=port_id@entry=0, mtu=<optimized out>) at
> ../lib/librte_ethdev/rte_ethdev.c:3484
> #4  0x00000000006a61d8 in update_jumbo_frame_offload
> (portid=portid@entry=0) at ../app/test-pmd/testpmd.c:3371
> #5  0x00000000006a62bc in init_config_port_offloads (pid=0,
> socket_id=0) at ../app/test-pmd/testpmd.c:1416
> #6  0x000000000061770c in init_config () at ../app/test-pmd/testpmd.c:1505
> #7  main (argc=<optimized out>, argv=<optimized out>) at
> ../app/test-pmd/testpmd.c:3800
> (gdb) f 1
> #1  0x0000000000e370d1 in virtio_check_scatter_on_all_rx_queues
> (frame_size=1530, dev=0x1799a40 <rte_eth_devices>) at
> ../drivers/net/virtio/virtio_ethdev.c:907
> 907            buf_size = virtio_rx_mem_pool_buf_size(rxvq->mpool);
> (gdb) p hw->max_queue_pairs
> $1 = 3
> (gdb) p qidx
> $2 = 5
> (gdb) p hw->vqs[0]
> $3 = (struct virtqueue *) 0x17ffb03c0
> (gdb) p hw->vqs[2]
> $4 = (struct virtqueue *) 0x17ff9dcc0
> (gdb) p hw->vqs[4]
> $5 = (struct virtqueue *) 0x17ff8acc0
> (gdb) p hw->vqs[6]
> $6 = (struct virtqueue *) 0x17ff77cc0
> (gdb) p hw->vqs[7]
> $7 = (struct virtqueue *) 0x0
> (gdb) p hw->vqs[8]
> $8 = (struct virtqueue *) 0x100004ac0
> (gdb) p hw->vqs[9]
> $9 = (struct virtqueue *) 0x17ffb1600
> (gdb) p hw->vqs[10]
> $10 = (struct virtqueue *) 0x17ffb18c0
> 
> 
> 

For reference, also observed when 20.11.3 is paired with OVS

https://mail.openvswitch.org/pipermail/ovs-dev/2021-September/387940.html