On Wed, Apr 24, 2024 at 03:57:04AM -0700, Konstantin Ovsepian wrote:
> From: Breno Leitao <lei...@debian.org>
>
> commit 059a49aa2e25c58f90b50151f109dd3c4cdb3a47 upstream
>
> There is a bug when setting the RSS options in virtio_net that can break
> the whole machine, getting the kernel into an infinite loop.
>
> Running the following command in any QEMU virtual machine with virtionet
> will reproduce this problem:
>
> # ethtool -X eth0 hfunc toeplitz
>
> This is how the problem happens:
>
> 1) ethtool_set_rxfh() calls virtnet_set_rxfh()
>
> 2) virtnet_set_rxfh() calls virtnet_commit_rss_command()
>
> 3) virtnet_commit_rss_command() populates 4 entries for the rss
> scatter-gather
>
> 4) Since the command above does not have a key, then the last
> scatter-gatter entry will be zeroed, since rss_key_size == 0.
> sg_buf_size = vi->rss_key_size;
>
> 5) This buffer is passed to qemu, but qemu is not happy with a buffer
> with zero length, and do the following in virtqueue_map_desc() (QEMU
> function):
>
> if (!sz) {
> virtio_error(vdev, "virtio: zero sized buffers are not allowed");
>
> 6) virtio_error() (also QEMU function) set the device as broken
>
> vdev->broken = true;
>
> 7) Qemu bails out, and do not repond this crazy kernel.
>
> 8) The kernel is waiting for the response to come back (function
> virtnet_send_command())
>
> 9) The kernel is waiting doing the following :
>
> while (!virtqueue_get_buf(vi->cvq, &tmp) &&
> !virtqueue_is_broken(vi->cvq))
> cpu_relax();
>
> 10) None of the following functions above is true, thus, the kernel
> loops here forever. Keeping in mind that virtqueue_is_broken() does
> not look at the qemu `vdev->broken`, so, it never realizes that the
> vitio is broken at QEMU side.
>
> Fix it by not sending RSS commands if the feature is not available in
> the device.
>
> Fixes: c7114b1249fa ("drivers/net/virtio_net: Added basic RSS support.")
> Cc: sta...@vger.kernel.org
> Cc: qemu-devel@nongnu.org
> Signed-off-by: Breno Leitao <lei...@debian.org>
> Reviewed-by: Heng Qi <hen...@linux.alibaba.com>
> Reviewed-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
> Signed-off-by: David S. Miller <da...@davemloft.net>
> (cherry picked from commit 059a49aa2e25c58f90b50151f109dd3c4cdb3a47)
> Signed-off-by: Konstantin Ovsepian <o...@ovs.to>
> ---
> drivers/net/virtio_net.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
Now queued up,t hanks.
greg k-h
