Bug 2309799 (CVE-2024-44968)

Summary: CVE-2024-44968 kernel: tick/broadcast: Move per CPU pointer access into the atomic section
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Bug Depends On: 2309818    
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Description OSIDB Bzimport 2024-09-04 19:21:20 UTC
In the Linux kernel, the following vulnerability has been resolved:

tick/broadcast: Move per CPU pointer access into the atomic section

The recent fix for making the take over of the broadcast timer more
reliable retrieves a per CPU pointer in preemptible context.

This went unnoticed as compilers hoist the access into the non-preemptible
region where the pointer is actually used. But of course it's valid that
the compiler keeps it at the place where the code puts it which rightfully
triggers:

  BUG: using smp_processor_id() in preemptible [00000000] code:
       caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0

Move it to the actual usage site which is in a non-preemptible region.