Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: powerpc/64s: Fix crashes when toggling entry flush barrier The entry flush mitigation can be enabled/disabled at runtime via a debugfs file (entry_flush), which causes the kernel to patch itself to enable/disable the relevant mitigations. However depending on which mitigation we're using, it may not be safe to do that patching while other CPUs are active. For example the following crash: sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20 Shows that we returned to userspace with a corrupted LR that points into the kernel, due to executing the partially patched call to the fallback entry flush (ie. we missed the LR restore). Fix it by doing the patching under stop machine. The CPUs that aren't doing the patching will be spinning in the core of the stop machine logic. That is currently sufficient for our purposes, because none of the patching we do is to that code or anywhere in the vicinity.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Linux | Linux Kernel | >= 4.4.245, < 4.4.269 |
References
- https://git.kernel.org/stable/c/0b4eb172cc12dc102cd0ad013e53ee4463db9508Patch
- https://git.kernel.org/stable/c/0c25a7bb697f2e6ee65b6d63782f675bf129511aPatch
- https://git.kernel.org/stable/c/2db22ba4e0e103f00e0512e0ecce36ac78c644f8Patch
- https://git.kernel.org/stable/c/5bc00fdda1e934c557351a9c751a205293e68cbfPatch
- https://git.kernel.org/stable/c/8382b15864e5014261b4f36c2aa89723612ee058Patch
- https://git.kernel.org/stable/c/aec86b052df6541cc97c5fca44e5934cbea4963bPatch
- https://git.kernel.org/stable/c/d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92Patch
- https://git.kernel.org/stable/c/dd0d6117052faace5440db20fc37175efe921c7dPatch
- https://git.kernel.org/stable/c/ee4b7aab93c2631c3bb0753023c5dda592bb666bPatch
- https://git.kernel.org/stable/c/0b4eb172cc12dc102cd0ad013e53ee4463db9508Patch
- https://git.kernel.org/stable/c/0c25a7bb697f2e6ee65b6d63782f675bf129511aPatch
- https://git.kernel.org/stable/c/2db22ba4e0e103f00e0512e0ecce36ac78c644f8Patch
- https://git.kernel.org/stable/c/5bc00fdda1e934c557351a9c751a205293e68cbfPatch
- https://git.kernel.org/stable/c/8382b15864e5014261b4f36c2aa89723612ee058Patch
- https://git.kernel.org/stable/c/aec86b052df6541cc97c5fca44e5934cbea4963bPatch
FAQ
What is CVE-2021-46990?
CVE-2021-46990 is a vulnerability with a CVSS score of 5.5 (MEDIUM). In the Linux kernel, the following vulnerability has been resolved: powerpc/64s: Fix crashes when toggling entry flush barrier The entry flush mitigation can be enabled/disabled at runtime via a deb...
How severe is CVE-2021-46990?
CVE-2021-46990 has been rated MEDIUM with a CVSS base score of 5.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-46990?
Check the references section above for vendor advisories and patch information. Affected products include: Linux Linux Kernel.