Bug 2320220 (CVE-2024-49856)

Summary: CVE-2024-49856 kernel: x86/sgx: Fix deadlock in SGX NUMA node search
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
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Hardware: All   
OS: Linux   
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Bug Depends On: 2320656    
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Description OSIDB Bzimport 2024-10-21 13:03:18 UTC 
In the Linux kernel, the following vulnerability has been resolved:

x86/sgx: Fix deadlock in SGX NUMA node search

When the current node doesn't have an EPC section configured by firmware
and all other EPC sections are used up, CPU can get stuck inside the
while loop that looks for an available EPC page from remote nodes
indefinitely, leading to a soft lockup. Note how nid_of_current will
never be equal to nid in that while loop because nid_of_current is not
set in sgx_numa_mask.

Also worth mentioning is that it's perfectly fine for the firmware not
to setup an EPC section on a node. While setting up an EPC section on
each node can enhance performance, it is not a requirement for
functionality.

Rework the loop to start and end on *a* node that has SGX memory. This
avoids the deadlock looking for the current SGX-lacking node to show up
in the loop when it never will.
Comment 1 Robb Gatica 2024-10-21 20:28:02 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2024102154-CVE-2024-49856-f5f7@gregkh/T
Comment 2 errata-xmlrpc 2025-05-13 08:29:11 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2025:6966 https://access.redhat.com/errata/RHSA-2025:6966