CVE-2021-46951

tpm: efi: Use local variable for calculating final log size

Severity Score

5.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Track

*SSVC

Descriptions

In the Linux kernel, the following vulnerability has been resolved:

tpm: efi: Use local variable for calculating final log size

When tpm_read_log_efi is called multiple times, which happens when
one loads and unloads a TPM2 driver multiple times, then the global
variable efi_tpm_final_log_size will at some point become a negative
number due to the subtraction of final_events_preboot_size occurring
each time. Use a local variable to avoid this integer underflow.

The following issue is now resolved:

Mar 8 15:35:12 hibinst kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Mar 8 15:35:12 hibinst kernel: Workqueue: tpm-vtpm vtpm_proxy_work [tpm_vtpm_proxy]
Mar 8 15:35:12 hibinst kernel: RIP: 0010:__memcpy+0x12/0x20
Mar 8 15:35:12 hibinst kernel: Code: 00 b8 01 00 00 00 85 d2 74 0a c7 05 44 7b ef 00 0f 00 00 00 c3 cc cc cc 66 66 90 66 90 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 f3 a4
Mar 8 15:35:12 hibinst kernel: RSP: 0018:ffff9ac4c0fcfde0 EFLAGS: 00010206
Mar 8 15:35:12 hibinst kernel: RAX: ffff88f878cefed5 RBX: ffff88f878ce9000 RCX: 1ffffffffffffe0f
Mar 8 15:35:12 hibinst kernel: RDX: 0000000000000003 RSI: ffff9ac4c003bff9 RDI: ffff88f878cf0e4d
Mar 8 15:35:12 hibinst kernel: RBP: ffff9ac4c003b000 R08: 0000000000001000 R09: 000000007e9d6073
Mar 8 15:35:12 hibinst kernel: R10: ffff9ac4c003b000 R11: ffff88f879ad3500 R12: 0000000000000ed5
Mar 8 15:35:12 hibinst kernel: R13: ffff88f878ce9760 R14: 0000000000000002 R15: ffff88f77de7f018
Mar 8 15:35:12 hibinst kernel: FS: 0000000000000000(0000) GS:ffff88f87bd00000(0000) knlGS:0000000000000000
Mar 8 15:35:12 hibinst kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Mar 8 15:35:12 hibinst kernel: CR2: ffff9ac4c003c000 CR3: 00000001785a6004 CR4: 0000000000060ee0
Mar 8 15:35:12 hibinst kernel: Call Trace:
Mar 8 15:35:12 hibinst kernel: tpm_read_log_efi+0x152/0x1a7
Mar 8 15:35:12 hibinst kernel: tpm_bios_log_setup+0xc8/0x1c0
Mar 8 15:35:12 hibinst kernel: tpm_chip_register+0x8f/0x260
Mar 8 15:35:12 hibinst kernel: vtpm_proxy_work+0x16/0x60 [tpm_vtpm_proxy]
Mar 8 15:35:12 hibinst kernel: process_one_work+0x1b4/0x370
Mar 8 15:35:12 hibinst kernel: worker_thread+0x53/0x3e0
Mar 8 15:35:12 hibinst kernel: ? process_one_work+0x370/0x370

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: tpm: efi: use la variable local para calcular el tamaño del registro final Cuando se llama a tpm_read_log_efi varias veces, lo que sucede cuando uno carga y descarga un controlador TPM2 varias veces, entonces la variable global efi_tpm_final_log_size en algún momento se convierte en un número negativo debido a la resta de final_events_preboot_size que ocurre cada vez. Utilice una variable local para evitar este desbordamiento de enteros. El siguiente problema ahora está resuelto: 8 de marzo 15:35:12 kernel hibinst: Nombre del hardware: PC estándar QEMU (Q35 + ICH9, 2009), BIOS 0.0.0 06/02/2015 8 de marzo 15:35:12 kernel hibinst: Cola de trabajo: tpm-vtpm vtpm_proxy_work [tpm_vtpm_proxy] 8 de marzo 15:35:12 kernel de hibinst: RIP: 0010:__memcpy+0x12/0x20 8 de marzo 15:35:12 kernel de hibinst: Código: 00 b8 01 00 00 00 85 d2 74 0a c7 05 44 7b ef 00 0f 00 00 00 c3 cc cc cc 66 66 90 66 90 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 f3 a4 8 de marzo 15:35:12 kernel de hibinst: RSP: 0018:ffff9ac4c0fcfde0 EFLAGS: 00010206 8 de marzo 15:35:12 kernel de hibinst: RAX: ffff88f878cefed5 RBX: ffff88f878ce9000 RCX: 1ff ffffffffffe0f 8 de marzo 15:35:12 kernel de hibinst: RDX: 0000000000000003 RSI: ffff9ac4c003bff9 RDI: ffff88f878cf0e4d 8 de marzo 15:35:12 kernel de hibinst: RBP: ffff9ac4c003b000 R08: 0000000000001000 R09: 000 000007e9d6073 8 de marzo 15:35:12 kernel hibinst: R10: ffff9ac4c003b000 R11: ffff88f879ad3500 R12: 0000000000000ed5 8 de marzo 15:35:12 kernel de hibinst: R13: ffff88f878ce9760 R14: 0000000000000002 R15: ffff88f77de7f018 8 de marzo 15:35:12 kernel de hibinst: FS: 0000000000000000(0000) GS:ffff8 8f87bd00000(0000) knlGS:0000000000000000 8 de marzo a las 15:35: 12 kernel de hibinst: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 8 de marzo 15:35:12 kernel de hibinst: CR2: ffff9ac4c003c000 CR3: 00000001785a6004 CR4: 0000000000060ee0 8 de marzo 15:35:12 kernel de hibinst: Seguimiento de llamadas: 8 de marzo 15:35:12 Hibinst Kernel: tpm_read_log_efi+0x152/0x1a7 mar 8 15:35:12 hibinst kernel: tpm_bios_log_setup+0xc8/0x1c0 mar 8 15:35:12 hibinst kernel: tpm_chip_register kernel de hibinst: vtpm_proxy_work+0x16/0x60 [tpm_vtpm_proxy] 8 de marzo 15:35:12 kernel de hibinst: Process_one_work+0x1b4/0x370 8 de marzo 15:35:12 kernel de hibinst: work_thread+0x53/0x3e0 8 de marzo 15:35:12 kernel de hibinst : ? proceso_un_trabajo+0x370/0x370

*Credits: N/A

CVSS Scores

NISTv3.1 5.5

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2024-02-25 CVE Reserved
2024-02-27 CVE Published
2024-04-21 EPSS Updated
2024-11-04 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-191: Integer Underflow (Wrap or Wraparound)

CAPEC

References (6)

URL	Tag	Source
https://git.kernel.org/stable/c/166a2809d65b282272c474835ec22c882a39ca1b	Vuln. Introduced

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/2f12258b5224cfaa808c54fd29345f3c1cbfca76	2021-05-11
https://git.kernel.org/stable/c/60a01ecc9f68067e4314a0b55148e39e5d58a51b	2021-05-11
https://git.kernel.org/stable/c/3818b753277f5ca0c170bf5b98e0a5a225542fcb	2021-05-12
https://git.kernel.org/stable/c/ac07c557ca12ec9276c0375517bac7ae5be4e50c	2021-05-12
https://git.kernel.org/stable/c/48cff270b037022e37835d93361646205ca25101	2021-04-14

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.3 < 5.4.118 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.4.118"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.3 < 5.10.36 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.10.36"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.3 < 5.11.20 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.11.20"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.3 < 5.12.3 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.12.3"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.3 < 5.13 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.13"		en		Affected