{
  "cveId": "CVE-2021-47531",
  "url": "https://patchblox.com/security/cve/CVE-2021-47531",
  "summary": "CVE-2021-47531 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47531, released May 24, 2024. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  drm/msm: Fix mmap to include VM_IO and VM_DONTDU...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  drm/msm: Fix mmap to include VM_IO and VM_DONTDUMP  In commit 510410bfc034 (\u0022drm/msm: Implement mmap as GEM object function\u0022) we switched to a new/cleaner method of doing things. That\u0027s good, but we missed a little bit.  Before that commit, we used to _first_ run through the drm_gem_mmap_obj() case where \u0060obj-\u003Efuncs-\u003Emmap()\u0060 was NULL. That meant that we ran:    vma-\u003Evm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;   vma-\u003Evm_page_prot = pgprot_writecombine(vm_get_page_prot(vma-\u003Evm_flags));   vma-\u003Evm_page_prot = pgprot_decrypted(vma-\u003Evm_page_prot);  ...and _then_ we modified those mappings with our own. Now that \u0060obj-\u003Efuncs-\u003Emmap()\u0060 is no longer NULL we don\u0027t run the default code. It looks like the fact that the vm_flags got VM_IO / VM_DONTDUMP was important because we\u0027re now getting crashes on Chromebooks that use ARC\u002B\u002B while logging out. Specifically a crash that looks like this (this is on a 5.10 kernel w/ relevant backports but also seen on a 5.15 kernel):    Unable to handle kernel paging request at virtual address ffffffc008000000   Mem abort info:     ESR = 0x96000006     EC = 0x25: DABT (current EL), IL = 32 bits     SET = 0, FnV = 0     EA = 0, S1PTW = 0   Data abort info:     ISV = 0, ISS = 0x00000006     CM = 0, WnR = 0   swapper pgtable: 4k pages, 39-bit VAs, pgdp=000000008293d000   [ffffffc008000000] pgd=00000001002b3003, p4d=00000001002b3003,                      pud=00000001002b3003, pmd=0000000000000000   Internal error: Oops: 96000006 [#1] PREEMPT SMP   [...]   CPU: 7 PID: 15734 Comm: crash_dump64 Tainted: G W 5.10.67 #1 [...]   Hardware name: Qualcomm Technologies, Inc. sc7280 IDP SKU2 platform (DT)   pstate: 80400009 (Nzcv daif \u002BPAN -UAO -TCO BTYPE=--)   pc : __arch_copy_to_user\u002B0xc0/0x30c   lr : copyout\u002B0xac/0x14c   [...]   Call trace:    __arch_copy_to_user\u002B0xc0/0x30c    copy_page_to_iter\u002B0x1a0/0x294    process_vm_rw_core\u002B0x240/0x408    process_vm_rw\u002B0x110/0x16c    __arm64_sys_process_vm_readv\u002B0x30/0x3c    el0_svc_common\u002B0xf8/0x250    do_el0_svc\u002B0x30/0x80    el0_svc\u002B0x10/0x1c    el0_sync_handler\u002B0x78/0x108    el0_sync\u002B0x184/0x1c0   Code: f8408423 f80008c3 910020c6 36100082 (b8404423)  Let\u0027s add the two flags back in.  While we\u0027re at it, the fact that we aren\u0027t running the default means that we _don\u0027t_ need to clear out VM_PFNMAP, so remove that and save an instruction.  NOTE: it was confirmed that VM_IO was the important flag to fix the problem I was seeing, but adding back VM_DONTDUMP seems like a sane thing to do so I\u0027m doing that too.",
  "published": "2024-05-24T15:15:16Z",
  "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": 0.00205,
  "epssPercentile": 0.10585,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "5.15.15-1",
      "fix": "DEBIAN-CVE-2021-47531",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47531",
      "released": "2024-05-24T15:15:16Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "5.15.15-1",
      "fix": "DEBIAN-CVE-2021-47531",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47531",
      "released": "2024-05-24T15:15:16Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "5.15.15-1",
      "fix": "DEBIAN-CVE-2021-47531",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47531",
      "released": "2024-05-24T15:15:16Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T19:12:23Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}