CVE-2022-48721: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-48721 is a vulnerability in the Linux kernel's SMC (Shared Memory Communication) networking component, discovered and disclosed in June 2024. The vulnerability affects the net/smc subsystem, specifically in how socket waitqueue entries are handled during TCP fallback operations (NVD).

The vulnerability occurs when TCP is replaced with SMC and a fallback occurs. Socket waitqueue entries (such as eppoll_entries inserted by userspace applications) remain in the smc socket->wq. After fallback, data flows over TCP/IP and only clcsocket->wq is woken up, preventing applications from being notified by entries inserted in smc socket->wq before fallback. The previous workaround of transferring entries from smc socket->wq to clcsock->wq during fallback could cause system crashes due to improper waitqueue entry management (Kernel Patch).

When exploited, this vulnerability can lead to system crashes due to general protection faults. The issue occurs because the owners of waitqueue entries (such as epoll) are unaware of entry transfers to different socket wait queues and continue using the original waitqueue spinlock, which no longer provides exclusive access (Kernel Patch).

The issue has been fixed by implementing a new mechanism that no longer transfers wait queue entries privately. Instead, it introduces custom implementations of clcsock's callback functions in fallback situations. These callback functions forward the wakeup to smc socket->wq if clcsock->wq is woken up and smc socket->wq has remaining entries (Kernel Patch).