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: 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.
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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2024-05-20T09:42:05.722Z

Updated: 2024-12-19T08:59:34.224Z

Reserved: 2024-05-17T13:50:33.144Z

Link: CVE-2024-35981

cve-icon Vulnrichment

Updated: 2024-08-02T03:21:49.058Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2024-05-20T10:15:12.617

Modified: 2024-11-21T09:21:21.163

Link: CVE-2024-35981

cve-icon Redhat

Severity : Low

Publid Date: 2024-05-20T00:00:00Z

Links: CVE-2024-35981 - Bugzilla