CVE-2023-52438

Description

In the Linux kernel, the following vulnerability has been resolved: binder: fix use-after-free in shinker's callback The mmap read lock is used during the shrinker's callback, which means that using alloc->vma pointer isn't safe as it can race with munmap(). As of commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") the mmap lock is downgraded after the vma has been isolated. I was able to reproduce this issue by manually adding some delays and triggering page reclaiming through the shrinker's debug sysfs. The following KASAN report confirms the UAF: ================================================================== BUG: KASAN: slab-use-after-free in zap_page_range_single+0x470/0x4b8 Read of size 8 at addr ffff356ed50e50f0 by task bash/478 CPU: 1 PID: 478 Comm: bash Not tainted 6.6.0-rc5-00055-g1c8b86a3799f-dirty #70 Hardware name: linux,dummy-virt (DT) Call trace: zap_page_range_single+0x470/0x4b8 binder_alloc_free_page+0x608/0xadc __list_lru_walk_one+0x130/0x3b0 list_lru_walk_node+0xc4/0x22c binder_shrink_scan+0x108/0x1dc shrinker_debugfs_scan_write+0x2b4/0x500 full_proxy_write+0xd4/0x140 vfs_write+0x1ac/0x758 ksys_write+0xf0/0x1dc __arm64_sys_write+0x6c/0x9c Allocated by task 492: kmem_cache_alloc+0x130/0x368 vm_area_alloc+0x2c/0x190 mmap_region+0x258/0x18bc do_mmap+0x694/0xa60 vm_mmap_pgoff+0x170/0x29c ksys_mmap_pgoff+0x290/0x3a0 __arm64_sys_mmap+0xcc/0x144 Freed by task 491: kmem_cache_free+0x17c/0x3c8 vm_area_free_rcu_cb+0x74/0x98 rcu_core+0xa38/0x26d4 rcu_core_si+0x10/0x1c __do_softirq+0x2fc/0xd24 Last potentially related work creation: __call_rcu_common.constprop.0+0x6c/0xba0 call_rcu+0x10/0x1c vm_area_free+0x18/0x24 remove_vma+0xe4/0x118 do_vmi_align_munmap.isra.0+0x718/0xb5c do_vmi_munmap+0xdc/0x1fc __vm_munmap+0x10c/0x278 __arm64_sys_munmap+0x58/0x7c Fix this issue by performing instead a vma_lookup() which will fail to find the vma that was isolated before the mmap lock downgrade. Note that this option has better performance than upgrading to a mmap write lock which would increase contention. Plus, mmap_write_trylock() has been recently removed anyway.

Gravité et risque d'exploitation

CVE-2023-52438 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 0.29 %, ce qui la place devant 20.8 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <9fa04c93f24138747807fe75b5591bb680098f56, 4.20, 5.15.148, 0, <a49087ab93508b60d9b8add91707a22dda832869, 6.8, <c8c1158ffb007197f31f9d9170cf13e4f34cbb5c, <4.20, 5.4.268, <=5.10.*, <=6.6.*, 6.7.1, <3f489c2067c5824528212b0fc18b28d51332d906, 6.1.74, <=5.4.*, dd2283f2605e3b3e9c61bcae844b34f2afa4813f, <8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6, <=*, <=5.15.*, 6.6.13, 5.10.209, <a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3, <=6.7.*, <e074686e993ff1be5f21b085a3b1b4275ccd5727) 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/a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3
• https://git.kernel.org/stable/c/c8c1158ffb007197f31f9d9170cf13e4f34cbb5c
• https://git.kernel.org/stable/c/8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6
• https://git.kernel.org/stable/c/9fa04c93f24138747807fe75b5591bb680098f56
• https://git.kernel.org/stable/c/a49087ab93508b60d9b8add91707a22dda832869
• https://git.kernel.org/stable/c/e074686e993ff1be5f21b085a3b1b4275ccd5727
• https://git.kernel.org/stable/c/3f489c2067c5824528212b0fc18b28d51332d906