{
  "cveId": "CVE-2021-47256",
  "url": "https://patchblox.com/security/cve/CVE-2021-47256",
  "summary": "CVE-2021-47256 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47256, released May 21, 2024. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  mm/memory-failure: make sure wait for page write...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  mm/memory-failure: make sure wait for page writeback in memory_failure  Our syzkaller trigger the \u0022BUG_ON(!list_empty(\u0026inode-\u003Ei_wb_list))\u0022 in clear_inode:    kernel BUG at fs/inode.c:519!   Internal error: Oops - BUG: 0 [#1] SMP   Modules linked in:   Process syz-executor.0 (pid: 249, stack limit = 0x00000000a12409d7)   CPU: 1 PID: 249 Comm: syz-executor.0 Not tainted 4.19.95   Hardware name: linux,dummy-virt (DT)   pstate: 80000005 (Nzcv daif -PAN -UAO)   pc : clear_inode\u002B0x280/0x2a8   lr : clear_inode\u002B0x280/0x2a8   Call trace:     clear_inode\u002B0x280/0x2a8     ext4_clear_inode\u002B0x38/0xe8     ext4_free_inode\u002B0x130/0xc68     ext4_evict_inode\u002B0xb20/0xcb8     evict\u002B0x1a8/0x3c0     iput\u002B0x344/0x460     do_unlinkat\u002B0x260/0x410     __arm64_sys_unlinkat\u002B0x6c/0xc0     el0_svc_common\u002B0xdc/0x3b0     el0_svc_handler\u002B0xf8/0x160     el0_svc\u002B0x10/0x218   Kernel panic - not syncing: Fatal exception  A crash dump of this problem show that someone called __munlock_pagevec to clear page LRU without lock_page: do_mmap -\u003E mmap_region -\u003E do_munmap -\u003E munlock_vma_pages_range -\u003E __munlock_pagevec.  As a result memory_failure will call identify_page_state without wait_on_page_writeback.  And after truncate_error_page clear the mapping of this page.  end_page_writeback won\u0027t call sb_clear_inode_writeback to clear inode-\u003Ei_wb_list.  That will trigger BUG_ON in clear_inode!  Fix it by checking PageWriteback too to help determine should we skip wait_on_page_writeback.",
  "published": "2024-05-21T15:15:14Z",
  "severity": "medium",
  "cvss": 5.5,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
  "epss": 0.00233,
  "epssPercentile": 0.14264,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "5.10.46-1",
      "fix": "DEBIAN-CVE-2021-47256",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47256",
      "released": "2024-05-21T15:15:14Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "5.10.46-1",
      "fix": "DEBIAN-CVE-2021-47256",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47256",
      "released": "2024-05-21T15:15:14Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "5.10.46-1",
      "fix": "DEBIAN-CVE-2021-47256",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47256",
      "released": "2024-05-21T15:15:14Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T07:25:28Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}