CVE-2026-53274

In the Linux kernel, the following vulnerability has been resolved:

net/smc: fix sleep-inside-lock in _smcsetsockopt() causing local DoS

A logic flaw in _smcsetsockopt() allows a local unprivileged user to cause a Denial of Service (DoS) by holding the socket lock indefinitely.

The function __smcsetsockopt() calls copyfromsockptr() while holding locksock(sk). By passing a userfaultfd-monitored memory page (or FUSE-backed memory on systems where unprivileged userfaultfd is disabled) as the optval, an attacker can halt execution during the copy operation, keeping the lock held.

Combined with asynchronous tear-down operations like shutdown(), this exhausts the kernel wq (kworkers) and triggers the hung task watchdog.

[ 240.123456] INFO: task kworker/u8:2 blocked for more than 120 seconds. [ 240.123489] Call Trace: [ 240.123501] smcshutdown+... [ 240.123512] locksock_nested+...

This patch moves the user-space copy outside the lock_sock() critical section to prevent the issue.