CVE-2024-56672

Description

In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: Fix UAF in blkcg_unpin_online() blkcg_unpin_online() walks up the blkcg hierarchy putting the online pin. To walk up, it uses blkcg_parent(blkcg) but it was calling that after blkcg_destroy_blkgs(blkcg) which could free the blkcg, leading to the following UAF: ================================================================== BUG: KASAN: slab-use-after-free in blkcg_unpin_online+0x15a/0x270 Read of size 8 at addr ffff8881057678c0 by task kworker/9:1/117 CPU: 9 UID: 0 PID: 117 Comm: kworker/9:1 Not tainted 6.13.0-rc1-work-00182-gb8f52214c61a-dirty #48 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022 Workqueue: cgwb_release cgwb_release_workfn Call Trace: <TASK> dump_stack_lvl+0x27/0x80 print_report+0x151/0x710 kasan_report+0xc0/0x100 blkcg_unpin_online+0x15a/0x270 cgwb_release_workfn+0x194/0x480 process_scheduled_works+0x71b/0xe20 worker_thread+0x82a/0xbd0 kthread+0x242/0x2c0 ret_from_fork+0x33/0x70 ret_from_fork_asm+0x1a/0x30 </TASK> ... Freed by task 1944: kasan_save_track+0x2b/0x70 kasan_save_free_info+0x3c/0x50 __kasan_slab_free+0x33/0x50 kfree+0x10c/0x330 css_free_rwork_fn+0xe6/0xb30 process_scheduled_works+0x71b/0xe20 worker_thread+0x82a/0xbd0 kthread+0x242/0x2c0 ret_from_fork+0x33/0x70 ret_from_fork_asm+0x1a/0x30 Note that the UAF is not easy to trigger as the free path is indirected behind a couple RCU grace periods and a work item execution. I could only trigger it with artifical msleep() injected in blkcg_unpin_online(). Fix it by reading the parent pointer before destroying the blkcg's blkg's.

Gravité et risque d'exploitation

CVE-2024-56672 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.27 %, ce qui la place devant 18.4 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions 6.13, <=6.1.*, <=6.12.*, 6.1.121, <29d1e06560f0f6179062ac638b4064deb637d1ad, 0, 5.10.234, 4308a434e5e08c78676aa66bc626ef78cbef0883, <64afc6fe24c9896c0153e5a199bcea241ecb0d5c, <8a07350fe070017a887433f4d6909433955be5f1, <5.7, <=5.10.*, <=6.6.*, <83f5a87ee8caa76a917f59912a74d6811f773c67, 5.15.177, <5baa28569c924d9a90d036c2aaab79f791fedaf8, 6.6.67, 5.7, <=*, <=5.15.*, 6.12.6, <86e6ca55b83c575ab0f2e105cf08f98e58d3d7af) 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/83f5a87ee8caa76a917f59912a74d6811f773c67
• https://git.kernel.org/stable/c/8a07350fe070017a887433f4d6909433955be5f1
• https://git.kernel.org/stable/c/64afc6fe24c9896c0153e5a199bcea241ecb0d5c
• https://git.kernel.org/stable/c/5baa28569c924d9a90d036c2aaab79f791fedaf8
• https://git.kernel.org/stable/c/29d1e06560f0f6179062ac638b4064deb637d1ad
• https://git.kernel.org/stable/c/86e6ca55b83c575ab0f2e105cf08f98e58d3d7af