CVE-2021-47640

  1. OpenCVE
  2. Vulnerabilities (CVE)
  3. CVE-2021-47640
In the Linux kernel, the following vulnerability has been resolved: powerpc/kasan: Fix early region not updated correctly The shadow's page table is not updated when PTE_RPN_SHIFT is 24 and PAGE_SHIFT is 12. It not only causes false positives but also false negative as shown the following text. Fix it by bringing the logic of kasan_early_shadow_page_entry here. 1. False Positive: ================================================================== BUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50 Write of size 16 at addr f57f3be0 by task swapper/0/1 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1 Call Trace: [c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable) [c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200 [c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570 [c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0 [c80d1db0] [c2036580] init_sd+0xc4/0x1d0 [c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c [c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernel_init+0x24/0x170 [c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64 Memory state around the buggy address: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 >f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ================================================================== 2. False Negative (with KASAN tests): ================================================================== Before fix: ok 45 - kmalloc_double_kzfree # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039 KASAN failure expected in "((volatile char *)area)[3100]", but none occurred not ok 46 - vmalloc_oob not ok 1 - kasan ================================================================== After fix: ok 1 - kasan

7.8 /10

CVSS v3 : HIGH

V3 Legend

Vector :

Exploitability : 1.8 / Impact : 5.9

Attack Vector LOCAL

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References
Link Resource
https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068 Patch
https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2 Patch
https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3 Patch
https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d Patch
https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6 Patch
https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115 Patch
Configurations

Configuration 1 (hide)

OR cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
History

18 Mar 2025, 19:09

Type Values Removed Values Added
CVSS v2 : unknown
v3 : unknown 		v2 : unknown
v3 : 7.8
First Time Linux
Linux linux Kernel
Summary
  • (es) En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: powerpc/kasan: Se solucionó que la región temprana no se actualizara correctamente La tabla de páginas de shadow no se actualiza cuando PTE_RPN_SHIFT es 24 y PAGE_SHIFT es 12. No solo causa falsos positivos sino también falsos negativos como se muestra en el siguiente texto. Arréglelo trayendo la lógica de kasan_early_shadow_page_entry aquí. 1. Falso positivo: ==================================================================== ERROR: KASAN: vmalloc fuera de los límites en pcpu_alloc+0x508/0xa50 Escritura de tamaño 16 en la dirección f57f3be0 por la tarea swapper/0/1 CPU: 0 PID: 1 Comm: swapper/0 No contaminado 5.15.0-12267-gdebe436e77c7 #1 Seguimiento de llamadas: [c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (no confiable) [c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200 [c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570 [c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0 [c80d1db0] [c2036580] init_sd+0xc4/0x1d0 [c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c [c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernel_init+0x24/0x170 [c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64 Estado de la memoria alrededor de la dirección con errores: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 >f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ===================================================================== 2. Falso negativo (con pruebas KASAN): ==================================================================== Antes de la corrección: ok 45 - kmalloc_double_kzfree # vmalloc_oob: EXPECTATIVA FALLÓ en lib/test_kasan.c:1039 Se esperaba una falla de KASAN en "((volatile char *)area)[3100]", pero no ocurrió ninguna no ok 46 - vmalloc_oob no ok 1 - kasan ======================================================================== Después de la corrección: ok 1 - kasan
CWE CWE-787
References () https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068 - () https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068 - Patch
References () https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2 - () https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2 - Patch
References () https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3 - () https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3 - Patch
References () https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d - () https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d - Patch
References () https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6 - () https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6 - Patch
References () https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115 - () https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115 - Patch
CPE cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

26 Feb 2025, 06:37

Type Values Removed Values Added
New CVE
Information

Published : 2025-02-26 06:37

Updated : 2025-03-18 19:09

NVD link : CVE-2021-47640

Mitre link : CVE-2021-47640

CVE.ORG link : CVE-2021-47640

JSON object : View

Products Affected

linux

  • linux_kernel
CWE
CWE-787

Out-of-bounds Write