{
  "affected": [
    {
      "database_specific": {
        "unresolved_ranges": [
          {
            "events": [
              {
                "introduced": "5.4"
              },
              {
                "fixed": "5.4.189"
              }
            ]
          },
          {
            "events": [
              {
                "introduced": "5.5"
              },
              {
                "fixed": "5.10.110"
              }
            ]
          },
          {
            "events": [
              {
                "introduced": "5.11"
              },
              {
                "fixed": "5.15.33"
              }
            ]
          },
          {
            "events": [
              {
                "introduced": "5.16"
              },
              {
                "fixed": "5.16.19"
              }
            ]
          },
          {
            "events": [
              {
                "introduced": "5.17"
              },
              {
                "fixed": "5.17.2"
              }
            ]
          }
        ]
      }
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/kasan: Fix early region not updated correctly\n\nThe shadow's page table is not updated when PTE_RPN_SHIFT is 24\nand PAGE_SHIFT is 12. It not only causes false positives but\nalso false negative as shown the following text.\n\nFix it by bringing the logic of kasan_early_shadow_page_entry here.\n\n1. False Positive:\n==================================================================\nBUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50\nWrite of size 16 at addr f57f3be0 by task swapper/0/1\n\nCPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1\nCall Trace:\n[c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable)\n[c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300\n[c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200\n[c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0\n[c80d1cc0] [c03018a4] memset+0x34/0x90\n[c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50\n[c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570\n[c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0\n[c80d1db0] [c2036580] init_sd+0xc4/0x1d0\n[c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c\n[c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384\n[c80d1ef0] [c0004b14] kernel_init+0x24/0x170\n[c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64\n\nMemory state around the buggy address:\n f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n\u003ef57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n                                               ^\n f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n==================================================================\n\n2. False Negative (with KASAN tests):\n==================================================================\nBefore fix:\n    ok 45 - kmalloc_double_kzfree\n    # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039\n    KASAN failure expected in \"((volatile char *)area)[3100]\", but none occurred\n    not ok 46 - vmalloc_oob\n    not ok 1 - kasan\n\n==================================================================\nAfter fix:\n    ok 1 - kasan",
  "id": "CVE-2021-47640",
  "modified": "2026-03-15T21:48:28.627678296Z",
  "published": "2025-02-26T06:37:05.780Z",
  "references": [
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}