A recently discovered vulnerability in the Linux Kernel's xen/netfront module has been patched to prevent potential crashes. This vulnerability, designated as CVE-2024-53240 or XSA-465, occurs when attempting to remove a netfront device immediately following a suspend/resume cycle.

In this blog post, we will dive into the details of the vulnerability, including examining the code changes necessary to resolve it and providing links to original references. We will also discuss the potential exploit associated with this vulnerability and how the fix addresses that risk.

Vulnerability Details

The bug in the Linux kernel's xen/netfront module occurs when attempting to remove a netfront device directly after a suspend/resume cycle. If the queues have not yet been set up again, this can result in a crash during the attempt to stop the queues a second time.

To fix this issue, the updated code checks if the queues exist before attempting to stop them.

The following patch was applied to kernel's xen/netfront module to resolve this vulnerability

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 731cd53..9f410a7 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1607,8 +1607,12 @@ static int xennet_disconnect_backend(struct net_device *dev)
 	nf = netdev_priv(dev);
 	np = &nf->netif;
 	
-	if (netif_running(dev))
+	if (netif_running(dev)) {
 		xennet_stop_queues(dev);
+		netif_device_detach(dev);
+	} else {
+		if (nf->queues)
+			xennet_stop_queues(dev);
 	}
 	
 	netdev_dbg(dev, "%s: Stopping queues to disconnect from backend.\n", __func__);

This patch checks if nf->queues exists in the xen-netfront.c file. If it does, xennet_stop_queues(dev) is called to stop the queues.

- CVE-2024-53240
- XSA-465
- Linux Kernel Patch

Exploit Details

An attacker who can initiate a suspend/resume cycle and then remove the netfront device during this window of opportunity could trigger a crash in the Linux kernel. This vulnerability could lead to a local denial of service or potentially escalate privileges through the exploitation of kernel memory corruption.

The patch mentioned above mitigates the risk of exploiting the vulnerability by checking for the existence of the queues before attempting to stop them, thus preventing the crash scenario.

Conclusion

This blog post has presented an overview of the CVE-2024-53240 vulnerabilities in the Linux kernel's xen/netfront module, along with the code changes necessary to resolve the issue, relevant links, and exploit details. By understanding the nature of this vulnerability and the patch's impact, users can better protect their systems and maintain a secure environment.

Timeline

Published on: 12/24/2024 10:15:06 UTC
Last modified on: 01/20/2025 06:21:53 UTC