CVE-2026-53274

Summary

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

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

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

The function __smc_setsockopt() calls copy_from_sockptr() while holding lock_sock(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] smc_shutdown+… [ 240.123512] lock_sock_nested+…

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

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/35a22117839602bb52283de08894c5a7dde92420
• https://git.kernel.org/stable/c/5d27d2ffe487df89ce28fda0410eafa05dbe03a0
• https://git.kernel.org/stable/c/89f6fbe0033c942cb790ffd53ca93a45eeaf1c91
• https://git.kernel.org/stable/c/dcd90f42a33e4220385f27b515183d0c91b2fc4a
• https://git.kernel.org/stable/c/94d286fa5eedc550d42bcb9c85416af8f77736ff
• https://git.kernel.org/stable/c/a3fdd924d88c30b9f488636ce0e4696012cf5511

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