CVE-2023-53368

Description

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix race issue between cpu buffer write and swap Warning happened in rb_end_commit() at code: if (RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing))) WARNING: CPU: 0 PID: 139 at kernel/trace/ring_buffer.c:3142 rb_commit+0x402/0x4a0 Call Trace: ring_buffer_unlock_commit+0x42/0x250 trace_buffer_unlock_commit_regs+0x3b/0x250 trace_event_buffer_commit+0xe5/0x440 trace_event_buffer_reserve+0x11c/0x150 trace_event_raw_event_sched_switch+0x23c/0x2c0 __traceiter_sched_switch+0x59/0x80 __schedule+0x72b/0x1580 schedule+0x92/0x120 worker_thread+0xa0/0x6f0 It is because the race between writing event into cpu buffer and swapping cpu buffer through file per_cpu/cpu0/snapshot: Write on CPU 0 Swap buffer by per_cpu/cpu0/snapshot on CPU 1 -------- -------- tracing_snapshot_write() [...] ring_buffer_lock_reserve() cpu_buffer = buffer->buffers[cpu]; // 1. Suppose find 'cpu_buffer_a'; [...] rb_reserve_next_event() [...] ring_buffer_swap_cpu() if (local_read(&cpu_buffer_a->committing)) goto out_dec; if (local_read(&cpu_buffer_b->committing)) goto out_dec; buffer_a->buffers[cpu] = cpu_buffer_b; buffer_b->buffers[cpu] = cpu_buffer_a; // 2. cpu_buffer has swapped here. rb_start_commit(cpu_buffer); if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { // 3. This check passed due to 'cpu_buffer->buffer' [...] // has not changed here. return NULL; } cpu_buffer_b->buffer = buffer_a; cpu_buffer_a->buffer = buffer_b; [...] // 4. Reserve event from 'cpu_buffer_a'. ring_buffer_unlock_commit() [...] cpu_buffer = buffer->buffers[cpu]; // 5. Now find 'cpu_buffer_b' !!! rb_commit(cpu_buffer) rb_end_commit() // 6. WARN for the wrong 'committing' state !!! Based on above analysis, we can easily reproduce by following testcase: ``` bash #!/bin/bash dmesg -n 7 sysctl -w kernel.panic_on_warn=1 TR=/sys/kernel/tracing echo 7 > ${TR}/buffer_size_kb echo "sched:sched_switch" > ${TR}/set_event while [ true ]; do echo 1 > ${TR}/per_cpu/cpu0/snapshot done & while [ true ]; do echo 1 > ${TR}/per_cpu/cpu0/snapshot done & while [ true ]; do echo 1 > ${TR}/per_cpu/cpu0/snapshot done & ``` To fix it, IIUC, we can use smp_call_function_single() to do the swap on the target cpu where the buffer is located, so that above race would be avoided.

Gravité et risque d'exploitation

CVE-2023-53368 obtient un score CVSS de 4.7/10, soit une gravité moyenne. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.14 %, ce qui la place devant 2.6 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <90e037cabc2c2dfc39b3dd9c5b22ea91f995539a, <3163f635b20e9e1fb4659e74f47918c9dddfe64e, f1affcaaa861f27752a769f889bf1486ebd301fe, <6182318ac04648b46db9d441fd7d696337fcdd0b, 0, <37ca1b686078b00cc4ffa008e2190615f7709b5d, <c5d30d6aa83d99fba8dfdd9cf6c4e4e7a63244db, <3.10, <=5.10.*, 6.5.3, 6.4.16, 5.4.257, <74c85396bd73eca80b96510b4edf93b9a3aff75f, 6.6, <=5.4.*, <89c89da92a60028013f9539be0dcce7e44405a43, 5.15.132, 5.10.195, <=*, <=5.15.*, <=6.5.*, 3.10, 6.1.53, <=6.4.*) 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/90e037cabc2c2dfc39b3dd9c5b22ea91f995539a
• https://git.kernel.org/stable/c/c5d30d6aa83d99fba8dfdd9cf6c4e4e7a63244db
• https://git.kernel.org/stable/c/6182318ac04648b46db9d441fd7d696337fcdd0b
• https://git.kernel.org/stable/c/74c85396bd73eca80b96510b4edf93b9a3aff75f
• https://git.kernel.org/stable/c/89c89da92a60028013f9539be0dcce7e44405a43
• https://git.kernel.org/stable/c/37ca1b686078b00cc4ffa008e2190615f7709b5d
• https://git.kernel.org/stable/c/3163f635b20e9e1fb4659e74f47918c9dddfe64e