CVE-2022-50516 : Détail

CVE-2022-50516

5.5
/
Moyen
Memory Corruption
0.03%V4
Local
2025-10-07
15h19 +00:00
2026-02-19
15h39 +00:00
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Descriptions du CVE

fs: dlm: fix invalid derefence of sb_lvbptr

In the Linux kernel, the following vulnerability has been resolved: fs: dlm: fix invalid derefence of sb_lvbptr I experience issues when putting a lkbsb on the stack and have sb_lvbptr field to a dangled pointer while not using DLM_LKF_VALBLK. It will crash with the following kernel message, the dangled pointer is here 0xdeadbeef as example: [ 102.749317] BUG: unable to handle page fault for address: 00000000deadbeef [ 102.749320] #PF: supervisor read access in kernel mode [ 102.749323] #PF: error_code(0x0000) - not-present page [ 102.749325] PGD 0 P4D 0 [ 102.749332] Oops: 0000 [#1] PREEMPT SMP PTI [ 102.749336] CPU: 0 PID: 1567 Comm: lock_torture_wr Tainted: G W 5.19.0-rc3+ #1565 [ 102.749343] Hardware name: Red Hat KVM/RHEL-AV, BIOS 1.16.0-2.module+el8.7.0+15506+033991b0 04/01/2014 [ 102.749344] RIP: 0010:memcpy_erms+0x6/0x10 [ 102.749353] Code: cc cc cc cc eb 1e 0f 1f 00 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 a4 c3 0f 1f 80 00 00 00 00 48 89 f8 48 83 fa 20 72 7e 40 38 fe [ 102.749355] RSP: 0018:ffff97a58145fd08 EFLAGS: 00010202 [ 102.749358] RAX: ffff901778b77070 RBX: 0000000000000000 RCX: 0000000000000040 [ 102.749360] RDX: 0000000000000040 RSI: 00000000deadbeef RDI: ffff901778b77070 [ 102.749362] RBP: ffff97a58145fd10 R08: ffff901760b67a70 R09: 0000000000000001 [ 102.749364] R10: ffff9017008e2cb8 R11: 0000000000000001 R12: ffff901760b67a70 [ 102.749366] R13: ffff901760b78f00 R14: 0000000000000003 R15: 0000000000000001 [ 102.749368] FS: 0000000000000000(0000) GS:ffff901876e00000(0000) knlGS:0000000000000000 [ 102.749372] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 102.749374] CR2: 00000000deadbeef CR3: 000000017c49a004 CR4: 0000000000770ef0 [ 102.749376] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 102.749378] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 102.749379] PKRU: 55555554 [ 102.749381] Call Trace: [ 102.749382] [ 102.749383] ? send_args+0xb2/0xd0 [ 102.749389] send_common+0xb7/0xd0 [ 102.749395] _unlock_lock+0x2c/0x90 [ 102.749400] unlock_lock.isra.56+0x62/0xa0 [ 102.749405] dlm_unlock+0x21e/0x330 [ 102.749411] ? lock_torture_stats+0x80/0x80 [dlm_locktorture] [ 102.749416] torture_unlock+0x5a/0x90 [dlm_locktorture] [ 102.749419] ? preempt_count_sub+0xba/0x100 [ 102.749427] lock_torture_writer+0xbd/0x150 [dlm_locktorture] [ 102.786186] kthread+0x10a/0x130 [ 102.786581] ? kthread_complete_and_exit+0x20/0x20 [ 102.787156] ret_from_fork+0x22/0x30 [ 102.787588] [ 102.787855] Modules linked in: dlm_locktorture torture rpcsec_gss_krb5 intel_rapl_msr intel_rapl_common kvm_intel iTCO_wdt iTCO_vendor_support kvm vmw_vsock_virtio_transport qxl irqbypass vmw_vsock_virtio_transport_common drm_ttm_helper crc32_pclmul joydev crc32c_intel ttm vsock virtio_scsi virtio_balloon snd_pcm drm_kms_helper virtio_console snd_timer snd drm soundcore syscopyarea i2c_i801 sysfillrect sysimgblt i2c_smbus pcspkr fb_sys_fops lpc_ich serio_raw [ 102.792536] CR2: 00000000deadbeef [ 102.792930] ---[ end trace 0000000000000000 ]--- This patch fixes the issue by checking also on DLM_LKF_VALBLK on exflags is set when copying the lvbptr array instead of if it's just null which fixes for me the issue. I think this patch can fix other dlm users as well, depending how they handle the init, freeing memory handling of sb_lvbptr and don't set DLM_LKF_VALBLK for some dlm_lock() calls. It might a there could be a hidden issue all the time. However with checking on DLM_LKF_VALBLK the user always need to provide a sb_lvbptr non-null value. There might be more intelligent handling between per ls lvblen, DLM_LKF_VALBLK and non-null to report the user the way how DLM API is used is wrong but can be added for later, this will only fix the current behaviour.

Informations du CVE

Faiblesses connexes

CWE-ID Nom de la faiblesse Source
CWE-476 NULL Pointer Dereference
The product dereferences a pointer that it expects to be valid but is NULL.

Métriques

Métriques Score Gravité CVSS Vecteur Source
V3.1 5.5 MEDIUM CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Local

The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities.

Attack Complexity

This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability.

Low

Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

Low

The attacker requires privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.

User Interaction

This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component.

None

The vulnerable system can be exploited without interaction from any user.

Base: Scope Metrics

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

None

There is no loss of confidentiality within the impacted component.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

None

There is no loss of integrity within the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

High

There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

nvd@nist.gov

EPSS

EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.

Score EPSS

Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.

Percentile EPSS

Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.

Products Mentioned

Configuraton 0

Linux>>Linux_kernel >> Version From (including) 2.6.19 To (excluding) 5.15.76

Linux>>Linux_kernel >> Version From (including) 5.16 To (excluding) 5.19.17

Linux>>Linux_kernel >> Version From (including) 6.0 To (excluding) 6.0.3

Références