Bug 1731283

Summary: L1TF CPU bug present and SMT on, data leak possible.
Product: [Fedora] Fedora Reporter: George R. Goffe <grgoffe>
Component: kernelAssignee: Kernel Maintainer List <kernel-maint>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: high Docs Contact:
Priority: unspecified    
Version: rawhideCC: airlied, bskeggs, hdegoede, ichavero, itamar, jarodwilson, jeremy, jglisse, john.j5live, jonathan, josef, kernel-maint, linville, mchehab, mjg59, steved
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Hardware: x86_64   
OS: Linux   
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Last Closed: 2019-07-18 22:40:29 UTC Type: Bug
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Description George R. Goffe 2019-07-18 22:34:25 UTC 
Created attachment 1591874 [details]
output of step 7 above (flat text file)

1. Please describe the problem: Received this message at the end of boot: L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.

System is FC 31 (x86_64 Rawhide)

2. What is the Version-Release number of the kernel:
5.3.0-0.rc0.git4.1.fc31.x86_64

3. Did it work previously in Fedora? If so, what kernel version did the issue
   *first* appear?  Old kernels are available for download at
   https://koji.fedoraproject.org/koji/packageinfo?packageID=8 :

This problem has come and gone for various kernels since fc 30 (rawhide)...

4. Can you reproduce this issue? If so, please provide the steps to reproduce
   the issue below:

The only thing I do is boot this system

5. Does this problem occur with the latest Rawhide kernel? To install the
   Rawhide kernel, run ``sudo dnf install fedora-repos-rawhide`` followed by
   ``sudo dnf update --enablerepo=rawhide kernel``:


6. Are you running any modules that not shipped with directly Fedora's kernel?:

Virtual Box

7. Please attach the kernel logs. You can get the complete kernel log
   for a boot with ``journalctl --no-hostname -k > dmesg.txt``. If the
   issue occurred on a previous boot, use the journalctl ``-b`` flag.
Comment 1 Matthew Garrett 2019-07-18 22:40:29 UTC 
This is expected behaviour. Your CPU suffers from the L1TF bug described in CVE-2018-3646. The only guaranteed way to avoid data leakage between processes running on the same physical core is to disable SMT. The kernel is simply warning you of this.
Comment 2 George R. Goffe 2019-07-19 04:41:53 UTC 
Matthew,

Thanks for the info.

George...