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Vulnerability · Published Feb 26, 2025 · Assigned by Linux

CVE-2021-47640powerpc/kasan: Fix early region not updated correctly

High 7.8

In plain English

A high-severity out-of-bounds write in Linux from Linux. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.8High
Exploit odds (30 days)0.3%top 82.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12linux5.17.3-1DEBIAN-CVE-2021-47640
Debian:13linux5.17.3-1DEBIAN-CVE-2021-47640
Debian:14linux5.17.3-1DEBIAN-CVE-2021-47640
Ubuntu:22.04:LTSlinux5.15.0-37.39UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-allwinner-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-aws5.15.0-1011.14UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-aws-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-aws-6.2no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-aws-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-azure5.15.0-1010.12UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-azure-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-azure-6.2no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-azure-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-azure-fde-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-azure-fde-6.2no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-gcp5.15.0-1008.12UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-gcp-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-gcp-6.2no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-gcp-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-gke5.15.0-1008.10UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-hwe-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-hwe-6.2no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-hwe-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-ibm5.15.0-1007.8UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-intel-iot-realtimeno fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-intel-iotg5.15.0-1008.11UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-kvm5.15.0-1010.11UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-lowlatency5.15.0-37.39UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-lowlatency-hwe-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.2no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-nvidia-6.2no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-nvidia-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-oem-5.17no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-oem-6.0no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-oem-6.1no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-oem-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-oracle5.15.0-1009.12UBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-oracle-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-raspi5.15.0-1011.13UBUNTU-CVE-2021-47640
Ubuntu:24.04:LTSlinux-raspi-realtimeno fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-riscv-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-riscv-6.5no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-starfive-5.19no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-starfive-6.2no fix listedUBUNTU-CVE-2021-47640
Ubuntu:22.04:LTSlinux-starfive-6.5no fix listedUBUNTU-CVE-2021-47640

Affected products (as reported)

VendorProductVersions
Linux Linux cbd18991e24fea2c31da3bb117c83e4a3538cd11 – before 7f19245c3647afea8c7c41f795506ef70f64b9f2cbd18991e24fea2c31da3bb117c83e4a3538cd11 – before f39a3309393a4a484532f6ba745c6acbcfe06115cbd18991e24fea2c31da3bb117c83e4a3538cd11 – before 5a3d8f3192a409893c57808cc935e16484df1068cbd18991e24fea2c31da3bb117c83e4a3538cd11 – before de56beace6648065d404cd9835aa7d30e3df519dcbd18991e24fea2c31da3bb117c83e4a3538cd11 – before e3d157a4b4f4e0268c98be5b7013bf4b31234bb6cbd18991e24fea2c31da3bb117c83e4a3538cd11 – before dd75080aa8409ce10d50fb58981c6b59bf8707d33822dd8c102d11ada9d9ed8e04cad0b347a046895.3.6 – before 5.4
Linux Linux 5.4

Weakness: CWE-787 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References