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x86/iopl: Cure TIF_IO_BITMAP inconsistencies

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: x86/iopl: Cure TIF_IO_BITMAP inconsistencies io_bitmap_exit() is invoked from exit_thread() when a task exists or when a fork fails. In the latter case the exit_thread() cleans up resources which were allocated during fork(). io_bitmap_exit() invokes task_update_io_bitmap(), which in turn ends up in tss_update_io_bitmap(). tss_update_io_bitmap() operates on the current task. If current has TIF_IO_BITMAP set, but no bitmap installed, tss_update_io_bitmap() crashes with a NULL pointer dereference. There are two issues, which lead to that problem: 1) io_bitmap_exit() should not invoke task_update_io_bitmap() when the task, which is cleaned up, is not the current task. That's a clear indicator for a cleanup after a failed fork(). 2) A task should not have TIF_IO_BITMAP set and neither a bitmap installed nor IOPL emulation level 3 activated. This happens when a kernel thread is created in the context of a user space thread, which has TIF_IO_BITMAP set as the thread flags are copied and the IO bitmap pointer is cleared. Other than in the failed fork() case this has no impact because kernel threads including IO workers never return to user space and therefore never invoke tss_update_io_bitmap(). Cure this by adding the missing cleanups and checks: 1) Prevent io_bitmap_exit() to invoke task_update_io_bitmap() if the to be cleaned up task is not the current task. 2) Clear TIF_IO_BITMAP in copy_thread() unconditionally

Announced Source revision 1
Original source ↗

CVE-2025-38100

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2025-38100

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "ea5f1cd7ab494f65f50f338299eabb40ad6a1767",
        "lessThan": "d64b7b05a827f98d068f412969eef65489b0cf03",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "ea5f1cd7ab494f65f50f338299eabb40ad6a1767",
        "lessThan": "2dace5e016c991424a3dc6e83b1ae5dca8992d08",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "ea5f1cd7ab494f65f50f338299eabb40ad6a1767",
        "lessThan": "aa5ce1485562f20235b4c759eee5ab0c41d2c220",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "ea5f1cd7ab494f65f50f338299eabb40ad6a1767",
        "lessThan": "2cfcbe1554c119402e7382de974c26b0549899fe",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "ea5f1cd7ab494f65f50f338299eabb40ad6a1767",
        "lessThan": "b3b3b6366dc8eb5b22edba9adc4bff3cdacfd64c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "ea5f1cd7ab494f65f50f338299eabb40ad6a1767",
        "lessThan": "73cfcc8445585b8af7e18be3c9246b851fdf336c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "ea5f1cd7ab494f65f50f338299eabb40ad6a1767",
        "lessThan": "8b68e978718f14fdcb080c2a7791c52a0d09bc6d",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "arch/x86/kernel/ioport.c",
      "arch/x86/kernel/process.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.5"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.5",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.239",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.186",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.142",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.94",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.34",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.15.3",
        "versionType": "semver",
        "lessThanOrEqual": "6.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.16",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "arch/x86/kernel/ioport.c",
      "arch/x86/kernel/process.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2025-38100

Source reference: /cveMetadata/cveId

Publisher severity

No explicit severity was provided.

Event
#27015 · Revision 1
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