CVE-2023-52887: Enhanced Error Handling for Tightly Received RTS Messages in Linux Kernel

In the Linux kernel, a vulnerability in the net: can: j1939 has been fixed through enhanced error handling capabilities. The issue arises in situations where Request to Send (RTS) messages arrive in close succession, which could potentially lead to unreliable communication. This article provides an overview of the vulnerability, the patch that addresses it, and some potential exploit scenarios.

The Vulnerability

The vulnerability exists in the Linux kernel's handling of tightly received RTS messages in the xtp_rx_rts_session_new process. Previously, problematic sessions were only released at the end of the j1939_xtp_rx_rts() function, which meant that communication could be disrupted during the session. Additionally, the earlier error handling mechanism employed WARN_ON_ONCE backtraces, which provided less informative feedback for developers and administrators.

The Patch

The patch enhances error handling by introducing a new method for managing tightly received RTS messages in xtp_rx_rts_session_new. This new approach provides clearer error messages and allows for the early termination of problematic sessions.

A possible way to reproduce the vulnerability before applying the patch is as follows

testj1939 -r vcan:x80 &
while true; do
	# send first RTS
	cansend vcan 18EC809#1014000303002301;
	# send second RTS
	cansend vcan 18EC809#1014000303002301;
	# send abort
	cansend vcan 18EC809#ff00000000002301;
done

This snippet tests the handling of simultaneous RTS messages by creating continuous test sessions on virtual CAN (vcan). After each session is created, RTS messages are sent in close succession and then followed by an abort command. The loop repeats indefinitely, potentially causing communication problems in an unpatched system.

Exploit Details

While there are no known exploits for this vulnerability, attackers with knowledge of the issue could potentially use it to cause disruption in systems that rely on the Linux kernel's J1939 implementation. By sending tightly received RTS messages, an attacker could cause confusion and breakdown in communication flows.

Original References

1. Linux Kernel Mailing List (LKML) – Patch announcement
2. Git commit applying the patch to the Linux kernel source code

Conclusion

This post has provided an overview of the CVE-2023-52887 vulnerability in the Linux kernel and the patch that addresses it. By updating to the latest version of the kernel and ensuring appropriate error handling is in place, system administrators and developers can mitigate the risk of communication issues caused by tightly-received RTS messages. Always keep your software up-to-date and follow best practices to protect your systems against known and unknown vulnerabilities.

Timeline

Published on: 07/29/2024 16:15:03 UTC
Last modified on: 12/19/2024 08:27:56 UTC