CVE-2024-35981 Affecting kernel-rt-trace-devel package, versions *
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Test your applications- Snyk ID SNYK-CENTOS7-KERNELRTTRACEDEVEL-6963025
- published 21 May 2024
- disclosed 20 May 2024
How to fix?
There is no fixed version for Centos:7 kernel-rt-trace-devel.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-rt-trace-devel package and not the kernel-rt-trace-devel package as distributed by Centos.
See How to fix? for Centos:7 relevant fixed versions and status.
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.
References
- https://access.redhat.com/security/cve/CVE-2024-35981
- https://git.kernel.org/stable/c/059a49aa2e25c58f90b50151f109dd3c4cdb3a47
- https://git.kernel.org/stable/c/28e9a64638cd16bc1ecac9ff74ffeacb9fb652de
- https://git.kernel.org/stable/c/43a71c1b4b3a6d4db857b1435d271540279fc7de
- https://git.kernel.org/stable/c/539a2b995a4ed93125cb0efae0f793b00ab2158b