CVE-2023-54086

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Add preempt_count_{sub,add} into btf id deny list The recursion check in __bpf_prog_enter* and __bpf_prog_exit* leave preempt_count_{sub,add} unprotected. When attaching trampoline to them we get panic as follows, [ 867.843050] BUG: TASK stack guard page was hit at 0000000009d325cf (stack is 0000000046a46a15..00000000537e7b28) [ 867.843064] stack guard page: 0000 [#1] PREEMPT SMP NOPTI [ 867.843067] CPU: 8 PID: 11009 Comm: trace Kdump: loaded Not tainted 6.2.0+ #4 [ 867.843100] Call Trace: [ 867.843101] <TASK> [ 867.843104] asm_exc_int3+0x3a/0x40 [ 867.843108] RIP: 0010:preempt_count_sub+0x1/0xa0 [ 867.843135] __bpf_prog_enter_recur+0x17/0x90 [ 867.843148] bpf_trampoline_6442468108_0+0x2e/0x1000 [ 867.843154] ? preempt_count_sub+0x1/0xa0 [ 867.843157] preempt_count_sub+0x5/0xa0 [ 867.843159] ? migrate_enable+0xac/0xf0 [ 867.843164] __bpf_prog_exit_recur+0x2d/0x40 [ 867.843168] bpf_trampoline_6442468108_0+0x55/0x1000 ... [ 867.843788] preempt_count_sub+0x5/0xa0 [ 867.843793] ? migrate_enable+0xac/0xf0 [ 867.843829] __bpf_prog_exit_recur+0x2d/0x40 [ 867.843837] BUG: IRQ stack guard page was hit at 0000000099bd8228 (stack is 00000000b23e2bc4..000000006d95af35) [ 867.843841] BUG: IRQ stack guard page was hit at 000000005ae07924 (stack is 00000000ffd69623..0000000014eb594c) [ 867.843843] BUG: IRQ stack guard page was hit at 00000000028320f0 (stack is 00000000034b6438..0000000078d1bcec) [ 867.843842] bpf_trampoline_6442468108_0+0x55/0x1000 ... That is because in __bpf_prog_exit_recur, the preempt_count_{sub,add} are called after prog->active is decreased. Fixing this by adding these two functions into btf ids deny list.

Gravité et risque d'exploitation

CVE-2023-54086 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 0.21 %, ce qui la place devant 10.3 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, 6.4, <60039bf72f81638baa28652a11a68e9b0b7b5b2d, <=*, 5.13, f5e770c0c60ab8812574a2e0d163b0efa816a825, <=5.15.*, <5.13, 6.3.4, <c11bd046485d7bf1ca200db0e7d0bdc4bafdd395, 5.12.11, 35e3815fa8102fab4dee75f3547472c66581125d, 5.15.113, 0, <b9168d41b83d182f34ba927ee822edaee18d5fc8, <=6.3.*, 6.1.30, <095018267c87b8bfbbb12eeb1c0ebf2359e1782c) 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/095018267c87b8bfbbb12eeb1c0ebf2359e1782c
• https://git.kernel.org/stable/c/60039bf72f81638baa28652a11a68e9b0b7b5b2d
• https://git.kernel.org/stable/c/b9168d41b83d182f34ba927ee822edaee18d5fc8
• https://git.kernel.org/stable/c/c11bd046485d7bf1ca200db0e7d0bdc4bafdd395