CVE-2021-46990
Vulnérabilité non évaluée dans Linux (Linux)
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.
Gravité et risque d'exploitation
CVE-2021-46990 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.23 %, ce qui la place devant 13.1 % des CVE référencées.
Que faire ?
- Vérifiez si Linux (versions <=5.11.*, <2db22ba4e0e103f00e0512e0ecce36ac78c644f8, 5.11.22, db01cad9efe3c3838a6b3a3f68affd295c4b92d6, 4.14.233, 4.9.269, f79643787e0a0762d2409b7b8334e83f22d85695, 4.4.269, fa4bf9f38184ed7ca4916eb64f8c767d1e279c1f, <4.19.191, 0, 5.10.38, 4.4.245, 4.9.245, <5bc00fdda1e934c557351a9c751a205293e68cbf, <0c25a7bb697f2e6ee65b6d63782f675bf129511a, <d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92, <=4.9.*, <=5.10.*, <=4.14.*, 5.4.79, <dd0d6117052faace5440db20fc37175efe921c7d, 5.9.10, f69bb4e51f41973fb7594be1479fa689831efe1a, <4.4.269, <4.14.233, 5.4.120, <=5.4.*, <ee4b7aab93c2631c3bb0753023c5dda592bb666b, <5.10, <=4.19.*, <=5.12.*, 5.13, 4.19.159, e590b36718d6e740b7b19514f710402a6499164c, <aec86b052df6541cc97c5fca44e5934cbea4963b, <5.4.120, 4.19.191, <=4.4.*, <4.9.269, <8382b15864e5014261b4f36c2aa89723612ee058, <=*, <0b4eb172cc12dc102cd0ad013e53ee4463db9508, 4a1e90af718d1489ffcecc8f52486c4f5dc0f7a6, b65458b6be8032c5179d4f562038575d7b3a6be3, 5.12.5, 4.14.208, 5.10) est présent sur votre parc.
- Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
- À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
- Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.
Références
- https://git.kernel.org/stable/c/8382b15864e5014261b4f36c2aa89723612ee058
- https://git.kernel.org/stable/c/0c25a7bb697f2e6ee65b6d63782f675bf129511a
- https://git.kernel.org/stable/c/ee4b7aab93c2631c3bb0753023c5dda592bb666b
- https://git.kernel.org/stable/c/2db22ba4e0e103f00e0512e0ecce36ac78c644f8
- https://git.kernel.org/stable/c/0b4eb172cc12dc102cd0ad013e53ee4463db9508
- https://git.kernel.org/stable/c/d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92
- https://git.kernel.org/stable/c/dd0d6117052faace5440db20fc37175efe921c7d
- https://git.kernel.org/stable/c/5bc00fdda1e934c557351a9c751a205293e68cbf
- https://git.kernel.org/stable/c/aec86b052df6541cc97c5fca44e5934cbea4963b