Bug 2492843 (CVE-2026-53274)

Summary: CVE-2026-53274 kernel: net/smc: fix sleep-inside-lock in __smc_setsockopt() causing local DoS
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's net/smc component. A local unprivileged user can exploit a logic flaw, specifically a 'sleep-inside-lock' issue within the __smc_setsockopt() function. By providing a specially crafted memory page, an attacker can cause the system to halt execution, leading to a Denial of Service (DoS) by exhausting kernel resources and triggering a hung task watchdog.
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Description OSIDB Bzimport 2026-06-25 10:08:38 UTC 
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.
Comment 1 Mauro Matteo Cascella 2026-06-25 16:44:31 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062519-CVE-2026-53274-dd59@gregkh/T