Linux Kernel NFSv4 Deadlock Vulnerability in State Recovery on Sillyrenamed Files

A deadlock vulnerability has been identified in the Linux kernel's NFSv4 implementation, specifically during the state recovery process for files that have been sillyrenamed. When such a file is marked for deletion upon closing, a server reboot can initiate an open reclaim process. This can conflict with an application's close() call, leading to a deadlock. The issue arises because the delegreturn call, triggered by the put_nfs_open_context() function, is not privileged, causing the deadlock. The vulnerability has been addressed by modifying the delegation return process to be asynchronous, preventing the deadlock scenario.

Impact

Exploitation of this vulnerability can lead to a deadlock situation, causing the system to hang and potentially disrupting NFS operations.