CVE-2021-46990
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…
Does this matter?
Lower severity and a low EPSS score (0.23%). Track it; it rarely justifies an emergency change on its own.
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 3.1
- 5.5 MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.23% probability · 14th percentile
- CISA KEV
- Not listed
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
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
- https://git.kernel.org/stable/c/d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92Patch
- https://git.kernel.org/stable/c/dd0d6117052faace5440db20fc37175efe921c7dPatch
- https://git.kernel.org/stable/c/ee4b7aab93c2631c3bb0753023c5dda592bb666bPatch
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.