Summary: Linux PV device frontends, including blkfront, netfront, scsifront, and others, are vulnerable to race conditions that can result in malicious backends triggering data leaks, data corruption, and denial of service (DoS) attacks. Here's an in-depth look into these vulnerabilities, their CVE assignments, and some exploit details.

The grant table interfaces used by several Linux PV device frontends, such as blkfront, netfront, scsifront, and the gntalloc driver, are vulnerable to race conditions. This can lead to potential data leaks, data corruption, and denial of service (DoS) attacks initiated by malicious backends. The mentioned vulnerabilities have been assigned the following CVEs:

xenbus: CVE-2022-23040

Vulnerable frontends like blkfront, netfront, scsifront, usbfront, dmabuf, xenbus, 9p, kbdfront, and pvcalls can be exploited to keep access to the shared memory page even after it has been freed and re-used for a different purpose. This particular vulnerability has been assigned CVE-2022-23041. To make matters worse, netfront can fail a BUG_ON() assertion if it fails to revoke access in the rx path. This failure leads to a guest-hosted denial of service (DoS) situation and has been assigned CVE-2022-23042.

/* Check grant ref is still in use */
if (gnttab_query_foreign_access(ref)) {
    // Proceed with the removal of granted access
    ...
} else {
    // Assume access removal will be successful without further checks
}

/* Remove granted access - vulnerable to race condition */
gnttab_end_foreign_access(ref, 1, page);


In this example, the grant reference check and the subsequent removal of granted access have a race condition. A malicious backend might map the granted page between these two steps and retain access to that memory page.

As shown by these vulnerabilities, it is crucial for developers, administrators, and users alike to be aware of these issues and apply necessary patches to secure their systems.

For more information on each of the vulnerabilities, refer to their respective CVE assignment pages

- CVE-2022-23036
- CVE-2022-23037
- CVE-2022-23038
- CVE-2022-23039
- CVE-2022-23040
- CVE-2022-23041
- CVE-2022-23042

In conclusion, these critical vulnerabilities in Linux PV device frontends expose systems to potential security breaches, emphasizing the importance of timely security patching and updates. If you are using any of the affected frontends, it is highly recommended to apply patches or workarounds to mitigate the risks.

Timeline

Published on: 03/10/2022 20:15:00 UTC
Last modified on: 07/01/2022 14:15:00 UTC