Linux Kernel TCP Race Condition Vulnerability in IPv6 Socket Handling

A race condition vulnerability has been identified in the Linux kernel's TCP implementation, specifically within the IPv6 socket handling. The issue arises in the 'tcp_v6_syn_recv_sock()' function, where the processing of child sockets after invoking 'tcp_v4_syn_recv_sock()' is delayed. This timing issue can lead to problems, as the child socket becomes visible in the TCP ehash table before it is fully initialized, potentially causing incorrect behavior when accessed by other CPUs. The vulnerability has been addressed by reorganizing the code to initialize the child socket properly before it is exposed to the ehash table, ensuring that it is ready for use and reducing the risk of interference from concurrent processes.

Impact

Exploitation of this vulnerability could lead to a race condition, where the timing of events can be manipulated, potentially causing incorrect behavior in TCP socket handling. This could disrupt normal network operations or, in a more severe scenario, be exploited to create a denial-of-service condition by causing sockets to be mishandled or improperly synchronized.

Reproduction

The vulnerability can be reproduced by creating a scenario where TCP sockets are handled concurrently across different CPUs. This can be achieved by sending TCP packets that trigger the 'tcp_v4_syn_recv_sock()' function, which will then call 'tcp_v6_syn_recv_sock()'. Due to the timing of these calls, the child socket in the IPv6 handler may not be fully initialized before it is accessed, leading to the race condition.

Remediation

Users can upgrade to the latest version of the Linux kernel where this vulnerability has been fixed. The specific commit addressing this issue is available in the Linux kernel stable tree.