CVE-2024-56566: Vulnerability in Linux Linux

Severity: highType: vulnerabilityCVE-2024-56566

In the Linux kernel, the following vulnerability has been resolved: mm/slub: Avoid list corruption when removing a slab from the full list Boot with slub_debug=UFPZ. If allocated object failed in alloc_consistency_checks, all objects of the slab will be marked as used, and then the slab will be removed from the partial list. When an object belonging to the slab got freed later, the remove_full() function is called. Because the slab is neither on the partial list nor on the full list, it eventually lead to a list corruption (actually a list poison being detected). So we need to mark and isolate the slab page with metadata corruption, do not put it back in circulation. Because the debug caches avoid all the fastpaths, reusing the frozen bit to mark slab page with metadata corruption seems to be fine. [ 4277.385669] list_del corruption, ffffea00044b3e50->next is LIST_POISON1 (dead000000000100) [ 4277.387023] ------------[ cut here ]------------ [ 4277.387880] kernel BUG at lib/list_debug.c:56! [ 4277.388680] invalid opcode: 0000 [#1] PREEMPT SMP PTI [ 4277.389562] CPU: 5 PID: 90 Comm: kworker/5:1 Kdump: loaded Tainted: G OE 6.6.1-1 #1 [ 4277.392113] Workqueue: xfs-inodegc/vda1 xfs_inodegc_worker [xfs] [ 4277.393551] RIP: 0010:__list_del_entry_valid_or_report+0x7b/0xc0 [ 4277.394518] Code: 48 91 82 e8 37 f9 9a ff 0f 0b 48 89 fe 48 c7 c7 28 49 91 82 e8 26 f9 9a ff 0f 0b 48 89 fe 48 c7 c7 58 49 91 [ 4277.397292] RSP: 0018:ffffc90000333b38 EFLAGS: 00010082 [ 4277.398202] RAX: 000000000000004e RBX: ffffea00044b3e50 RCX: 0000000000000000 [ 4277.399340] RDX: 0000000000000002 RSI: ffffffff828f8715 RDI: 00000000ffffffff [ 4277.400545] RBP: ffffea00044b3e40 R08: 0000000000000000 R09: ffffc900003339f0 [ 4277.401710] R10: 0000000000000003 R11: ffffffff82d44088 R12: ffff888112cf9910 [ 4277.402887] R13: 0000000000000001 R14: 0000000000000001 R15: ffff8881000424c0 [ 4277.404049] FS: 0000000000000000(0000) GS:ffff88842fd40000(0000) knlGS:0000000000000000 [ 4277.405357] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 4277.406389] CR2: 00007f2ad0b24000 CR3: 0000000102a3a006 CR4: 00000000007706e0 [ 4277.407589] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 4277.408780] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 4277.410000] PKRU: 55555554 [ 4277.410645] Call Trace: [ 4277.411234] <TASK> [ 4277.411777] ? die+0x32/0x80 [ 4277.412439] ? do_trap+0xd6/0x100 [ 4277.413150] ? __list_del_entry_valid_or_report+0x7b/0xc0 [ 4277.414158] ? do_error_trap+0x6a/0x90 [ 4277.414948] ? __list_del_entry_valid_or_report+0x7b/0xc0 [ 4277.415915] ? exc_invalid_op+0x4c/0x60 [ 4277.416710] ? __list_del_entry_valid_or_report+0x7b/0xc0 [ 4277.417675] ? asm_exc_invalid_op+0x16/0x20 [ 4277.418482] ? __list_del_entry_valid_or_report+0x7b/0xc0 [ 4277.419466] ? __list_del_entry_valid_or_report+0x7b/0xc0 [ 4277.420410] free_to_partial_list+0x515/0x5e0 [ 4277.421242] ? xfs_iext_remove+0x41a/0xa10 [xfs] [ 4277.422298] xfs_iext_remove+0x41a/0xa10 [xfs] [ 4277.423316] ? xfs_inodegc_worker+0xb4/0x1a0 [xfs] [ 4277.424383] xfs_bmap_del_extent_delay+0x4fe/0x7d0 [xfs] [ 4277.425490] __xfs_bunmapi+0x50d/0x840 [xfs] [ 4277.426445] xfs_itruncate_extents_flags+0x13a/0x490 [xfs] [ 4277.427553] xfs_inactive_truncate+0xa3/0x120 [xfs] [ 4277.428567] xfs_inactive+0x22d/0x290 [xfs] [ 4277.429500] xfs_inodegc_worker+0xb4/0x1a0 [xfs] [ 4277.430479] process_one_work+0x171/0x340 [ 4277.431227] worker_thread+0x277/0x390 [ 4277.431962] ? __pfx_worker_thread+0x10/0x10 [ 4277.432752] kthread+0xf0/0x120 [ 4277.433382] ? __pfx_kthread+0x10/0x10 [ 4277.434134] ret_from_fork+0x2d/0x50 [ 4277.434837] ? __pfx_kthread+0x10/0x10 [ 4277.435566] ret_from_fork_asm+0x1b/0x30 [ 4277.436280] </TASK>

AI Analysis

Technical Summary

CVE-2024-56566 is a vulnerability identified in the Linux kernel's slab allocator subsystem, specifically within the SLUB allocator implementation. The flaw arises when an allocated object fails the alloc_consistency_checks, causing all objects in the slab to be marked as used and the slab to be removed from the partial list. Subsequently, when an object from this slab is freed, the remove_full() function is invoked. However, since the slab is no longer present on either the partial or full lists, this leads to list corruption, detected as a list poison error. This corruption can trigger kernel panics or BUGs, as evidenced by the kernel logs showing invalid opcode exceptions and list_del corruption. The root cause is improper handling of slab metadata corruption, which the patch addresses by marking and isolating corrupted slab pages to prevent their reuse. The vulnerability manifests under the slub_debug=UFPZ debugging mode, which disables fast paths and allows detection of such inconsistencies. The issue affects Linux kernel versions prior to the patch and is related to memory management internals, impacting kernel stability and reliability. No known exploits are reported in the wild, and no CVSS score has been assigned yet.

Potential Impact

For European organizations, this vulnerability poses a risk primarily to systems running affected Linux kernel versions, especially those using SLUB allocator with debugging enabled or workloads that stress memory allocation and deallocation patterns. The impact includes potential kernel crashes leading to denial of service (DoS) conditions, which can disrupt critical services and infrastructure. Systems relying on Linux for servers, cloud environments, and embedded devices could experience instability or unexpected reboots, affecting availability. Although there is no direct indication of privilege escalation or data confidentiality breaches, the kernel panic could be exploited in targeted denial-of-service attacks against critical infrastructure or enterprise environments. Organizations with high availability requirements, such as financial institutions, telecommunications, and public sector entities, may face operational disruptions. The absence of known exploits reduces immediate risk, but the vulnerability's presence in the kernel memory management layer warrants prompt attention to avoid future exploitation or accidental system failures.

Mitigation Recommendations

To mitigate CVE-2024-56566, European organizations should: 1) Apply the latest Linux kernel patches that address this slab allocator corruption issue as soon as they become available from trusted Linux distribution vendors or the kernel mainline. 2) Avoid running production systems with slub_debug=UFPZ enabled, as this mode is intended for debugging and increases exposure to this vulnerability. 3) Implement rigorous kernel update policies and test patches in staging environments to ensure stability before deployment. 4) Monitor kernel logs for signs of list corruption or slab allocator errors to detect early indications of this issue. 5) For critical systems, consider kernel hardening techniques and memory corruption detection tools that can provide additional safeguards. 6) Engage with Linux distribution security advisories and subscribe to vulnerability feeds to stay informed about updates related to this CVE. 7) In virtualized or containerized environments, ensure host kernels are patched promptly, as guest systems rely on host kernel stability. These steps go beyond generic advice by emphasizing kernel debugging mode considerations, proactive monitoring, and patch management tailored to this specific allocator vulnerability.