CVE-2024-39488
CVE Descriptions
arm64: asm-bug: Add .align 2 to the end of __BUG_ENTRY
In the Linux kernel, the following vulnerability has been resolved: arm64: asm-bug: Add .align 2 to the end of __BUG_ENTRY When CONFIG_DEBUG_BUGVERBOSE=n, we fail to add necessary padding bytes to bug_table entries, and as a result the last entry in a bug table will be ignored, potentially leading to an unexpected panic(). All prior entries in the table will be handled correctly. The arm64 ABI requires that struct fields of up to 8 bytes are naturally-aligned, with padding added within a struct such that struct are suitably aligned within arrays. When CONFIG_DEBUG_BUGVERPOSE=y, the layout of a bug_entry is: struct bug_entry { signed int bug_addr_disp; // 4 bytes signed int file_disp; // 4 bytes unsigned short line; // 2 bytes unsigned short flags; // 2 bytes } ... with 12 bytes total, requiring 4-byte alignment. When CONFIG_DEBUG_BUGVERBOSE=n, the layout of a bug_entry is: struct bug_entry { signed int bug_addr_disp; // 4 bytes unsigned short flags; // 2 bytes < implicit padding > // 2 bytes } ... with 8 bytes total, with 6 bytes of data and 2 bytes of trailing padding, requiring 4-byte alginment. When we create a bug_entry in assembly, we align the start of the entry to 4 bytes, which implicitly handles padding for any prior entries. However, we do not align the end of the entry, and so when CONFIG_DEBUG_BUGVERBOSE=n, the final entry lacks the trailing padding bytes. For the main kernel image this is not a problem as find_bug() doesn't depend on the trailing padding bytes when searching for entries: for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) if (bugaddr == bug_addr(bug)) return bug; However for modules, module_bug_finalize() depends on the trailing bytes when calculating the number of entries: mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); ... and as the last bug_entry lacks the necessary padding bytes, this entry will not be counted, e.g. in the case of a single entry: sechdrs[i].sh_size == 6 sizeof(struct bug_entry) == 8; sechdrs[i].sh_size / sizeof(struct bug_entry) == 0; Consequently module_find_bug() will miss the last bug_entry when it does: for (i = 0; i < mod->num_bugs; ++i, ++bug) if (bugaddr == bug_addr(bug)) goto out; ... which can lead to a kenrel panic due to an unhandled bug. This can be demonstrated with the following module: static int __init buginit(void) { WARN(1, "hello\n"); return 0; } static void __exit bugexit(void) { } module_init(buginit); module_exit(bugexit); MODULE_LICENSE("GPL"); ... which will trigger a kernel panic when loaded: ------------[ cut here ]------------ hello Unexpected kernel BRK exception at EL1 Internal error: BRK handler: 00000000f2000800 [#1] PREEMPT SMP Modules linked in: hello(O+) CPU: 0 PID: 50 Comm: insmod Tainted: G O 6.9.1 #8 Hardware name: linux,dummy-virt (DT) pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : buginit+0x18/0x1000 [hello] lr : buginit+0x18/0x1000 [hello] sp : ffff800080533ae0 x29: ffff800080533ae0 x28: 0000000000000000 x27: 0000000000000000 x26: ffffaba8c4e70510 x25: ffff800080533c30 x24: ffffaba8c4a28a58 x23: 0000000000000000 x22: 0000000000000000 x21: ffff3947c0eab3c0 x20: ffffaba8c4e3f000 x19: ffffaba846464000 x18: 0000000000000006 x17: 0000000000000000 x16: ffffaba8c2492834 x15: 0720072007200720 x14: 0720072007200720 x13: ffffaba8c49b27c8 x12: 0000000000000312 x11: 0000000000000106 x10: ffffaba8c4a0a7c8 x9 : ffffaba8c49b27c8 x8 : 00000000ffffefff x7 : ffffaba8c4a0a7c8 x6 : 80000000fffff000 x5 : 0000000000000107 x4 : 0000000000000000 x3 : 0000000000000000 x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff3947c0eab3c0 Call trace: buginit+0x18/0x1000 [hello] do_one_initcall+0x80/0x1c8 do_init_module+0x60/0x218 load_module+0x1ba4/0x1d70 __do_sys_init_module+0x198/0x1d0 __arm64_sys_init_module+0x1c/0x28 invoke_syscall+0x48/0x114 el0_svc ---truncated---CVE Informations
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 MetricsThe 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 MetricsThe 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 MetricsThe 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 MetricsThe 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 MetricsThese 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 Score
EPSS Percentile
Products Mentioned
Configuraton 0
Linux>>Linux_kernel >> Version From (including) 4.3 To (excluding) 4.19.316
Linux>>Linux_kernel >> Version From (including) 4.20 To (excluding) 5.4.278
Linux>>Linux_kernel >> Version From (including) 5.5 To (excluding) 5.10.219
Linux>>Linux_kernel >> Version From (including) 5.11 To (excluding) 5.15.161
Linux>>Linux_kernel >> Version From (including) 5.16 To (excluding) 6.1.93
Linux>>Linux_kernel >> Version From (including) 6.2 To (excluding) 6.6.33
Linux>>Linux_kernel >> Version From (including) 6.7 To (excluding) 6.9.4
