CVE Descriptions

In the Linux kernel, the following vulnerability has been resolved: rbd: fix null-ptr-deref when device_add_disk() fails do_rbd_add() publishes the device with device_add() before calling device_add_disk(). If device_add_disk() fails after device_add() succeeds, the error path calls rbd_free_disk() directly and then later falls through to rbd_dev_device_release(), which calls rbd_free_disk() again. This double teardown can leave blk-mq cleanup operating on invalid state and trigger a null-ptr-deref in __blk_mq_free_map_and_rqs(), reached from blk_mq_free_tag_set(). Fix this by following the normal remove ordering: call device_del() before rbd_dev_device_release() when device_add_disk() fails after device_add(). That keeps the teardown sequence consistent and avoids re-entering disk cleanup through the wrong path. The bug was first flagged by an experimental analysis tool we are developing for kernel memory-management bugs while analyzing v6.13-rc1. The tool is still under development and is not yet publicly available. We reproduced the bug on v7.0 with a real Ceph backend and a QEMU x86_64 guest booted with KASAN and CONFIG_FAILSLAB enabled. The reproducer confines failslab injections to the __add_disk() range and injects fail-nth while mapping an RBD image through /sys/bus/rbd/add_single_major. On the unpatched kernel, fail-nth=4 reliably triggered the fault: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 UID: 0 PID: 273 Comm: bash Not tainted 7.0.0-01247-gd60bc1401583 #6 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 RIP: 0010:__blk_mq_free_map_and_rqs+0x8c/0x240 Code: 00 00 48 8b 6b 60 41 89 f4 49 c1 e4 03 4c 01 e5 45 85 ed 0f 85 0a 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 e9 48 c1 e9 03 <80> 3c 01 00 0f 85 31 01 00 00 4c 8b 6d 00 4d 85 ed 0f 84 e2 00 00 RSP: 0018:ff1100000ab0fac8 EFLAGS: 00000246 RAX: dffffc0000000000 RBX: ff1100000c4806a0 RCX: 0000000000000000 RDX: 0000000000000002 RSI: 0000000000000000 RDI: ff1100000c4806f4 RBP: 0000000000000000 R08: 0000000000000001 R09: ffe21c000189001b R10: ff1100000c4800df R11: ff1100006cf37be0 R12: 0000000000000000 R13: 0000000000000000 R14: ff1100000c480700 R15: ff1100000c480004 FS: 00007f0fbe8fe740(0000) GS:ff110000e5851000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe53473b2e0 CR3: 0000000012eef000 CR4: 00000000007516f0 PKRU: 55555554 Call Trace: blk_mq_free_tag_set+0x77/0x460 do_rbd_add+0x1446/0x2b80 ? __pfx_do_rbd_add+0x10/0x10 ? lock_acquire+0x18c/0x300 ? find_held_lock+0x2b/0x80 ? sysfs_file_kobj+0xb6/0x1b0 ? __pfx_sysfs_kf_write+0x10/0x10 kernfs_fop_write_iter+0x2f4/0x4a0 vfs_write+0x98e/0x1000 ? expand_files+0x51f/0x850 ? __pfx_vfs_write+0x10/0x10 ksys_write+0xf2/0x1d0 ? __pfx_ksys_write+0x10/0x10 do_syscall_64+0x115/0x690 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f0fbea15907 Code: 10 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24 RSP: 002b:00007ffe22346ea8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000058 RCX: 00007f0fbea15907 RDX: 0000000000000058 RSI: 0000563ace6c0ef0 RDI: 0000000000000001 RBP: 0000563ace6c0ef0 R08: 0000563ace6c0ef0 R09: 6b6435726d694141 R10: 5250337279762f78 R11: 0000000000000246 R12: 0000000000000058 R13: 00007f0fbeb1c780 R14: ff1100000c480700 R15: ff1100000c480004 With this fix applied, rerunning the reproducer over fail-nth=1..256 yields no KASAN reports. [ idryomov: rename err_out_device_del -> err_out_device ]

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-476	NULL Pointer Dereference The product dereferences a pointer that it expects to be valid but is NULL.

Metrics

Metrics	Score	Severity	CVSS Vector	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 More informations 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 is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

EPSS First.org