CVE-2021-47603

Description

In the Linux kernel, the following vulnerability has been resolved: audit: improve robustness of the audit queue handling If the audit daemon were ever to get stuck in a stopped state the kernel's kauditd_thread() could get blocked attempting to send audit records to the userspace audit daemon. With the kernel thread blocked it is possible that the audit queue could grow unbounded as certain audit record generating events must be exempt from the queue limits else the system enter a deadlock state. This patch resolves this problem by lowering the kernel thread's socket sending timeout from MAX_SCHEDULE_TIMEOUT to HZ/10 and tweaks the kauditd_send_queue() function to better manage the various audit queues when connection problems occur between the kernel and the audit daemon. With this patch, the backlog may temporarily grow beyond the defined limits when the audit daemon is stopped and the system is under heavy audit pressure, but kauditd_thread() will continue to make progress and drain the queues as it would for other connection problems. For example, with the audit daemon put into a stopped state and the system configured to audit every syscall it was still possible to shutdown the system without a kernel panic, deadlock, etc.; granted, the system was slow to shutdown but that is to be expected given the extreme pressure of recording every syscall. The timeout value of HZ/10 was chosen primarily through experimentation and this developer's "gut feeling". There is likely no one perfect value, but as this scenario is limited in scope (root privileges would be needed to send SIGSTOP to the audit daemon), it is likely not worth exposing this as a tunable at present. This can always be done at a later date if it proves necessary.

Gravité et risque d'exploitation

CVE-2021-47603 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 0.18 %, ce qui la place devant 7.2 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions 5.15.11, 4.10.7, 5.16, a0c48115cd2343231585f2f5e609b2ac9aa4e0af, 4.11, 0, 5.4.168, <0d3277eabd542fb662be23696e5ec9f390d688e1, <a5f4d17daf2e6cd7c1d9676b476147f6b4ac53f2, <=5.10.*, <=4.14.*, 5.10.88, 5b52330bbfe63b3305765354d6046c9f7f89c011, <=5.4.*, <4.11, <=4.19.*, 4.19.222, <f4b3ee3c85551d2d343a3ba159304066523f730f, <=*, <=5.15.*, <4cc6badff97f74d0fce65f9784b5df3b64e4250b, <75fdb751f84727d614deea0571a1490c3225d83a, <8389f50ceb854cb437fefb9330d5024ed3c7c1f5, 4.14.259) 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/75fdb751f84727d614deea0571a1490c3225d83a
• https://git.kernel.org/stable/c/8389f50ceb854cb437fefb9330d5024ed3c7c1f5
• https://git.kernel.org/stable/c/0d3277eabd542fb662be23696e5ec9f390d688e1
• https://git.kernel.org/stable/c/4cc6badff97f74d0fce65f9784b5df3b64e4250b
• https://git.kernel.org/stable/c/a5f4d17daf2e6cd7c1d9676b476147f6b4ac53f2
• https://git.kernel.org/stable/c/f4b3ee3c85551d2d343a3ba159304066523f730f