In the Linux kernel, the following vulnerability has been resolved:
virtio_net: Do not send RSS key if it is not supported
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:
ethtool_set_rxfh() calls virtnet_set_rxfh()
virtnet_set_rxfh() calls virtnet_commit_rss_command()
virtnet_commit_rss_command() populates 4 entries for the rss
scatter-gather
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;
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”);
virtio_error() (also QEMU function) set the device as broken
vdev->broken = true;
Qemu bails out, and do not repond this crazy kernel.
The kernel is waiting for the response to come back (function
virtnet_send_command())
The kernel is waiting doing the following :
while (!virtqueue_get_buf(vi->cvq, &tmp) &&
!virtqueue_is_broken(vi->cvq))
cpu_relax();
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.
[
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"drivers/net/virtio_net.c"
],
"versions": [
{
"version": "c7114b1249fa",
"lessThan": "539a2b995a4e",
"status": "affected",
"versionType": "git"
},
{
"version": "c7114b1249fa",
"lessThan": "43a71c1b4b3a",
"status": "affected",
"versionType": "git"
},
{
"version": "c7114b1249fa",
"lessThan": "28e9a64638cd",
"status": "affected",
"versionType": "git"
},
{
"version": "c7114b1249fa",
"lessThan": "059a49aa2e25",
"status": "affected",
"versionType": "git"
}
]
},
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"drivers/net/virtio_net.c"
],
"versions": [
{
"version": "5.18",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.18",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.1.90",
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.6.29",
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.8.7",
"lessThanOrEqual": "6.8.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.9",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
]