CVE-2021-47491

Summary

In the Linux kernel, the following vulnerability has been resolved:

mm: khugepaged: skip huge page collapse for special files

The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2].

This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface.

[shy828301@gmail.com: fix vm_file check [3]]

Affected Software

VendorProductVersion RangeStatus
LinuxLinux99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 < 6d67b2a73b8e3a079c355bab3c1aef7d85a044b8affected
LinuxLinux99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 < 5fcb6fce74ffa614d964667110cf1a516c48c6d9affected
LinuxLinux99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 < a4aeaa06d45e90f9b279f0b09de84bd00006e733affected
LinuxLinux5.4affected
LinuxLinux0 < 5.4unaffected
LinuxLinux5.10.78 <= 5.10.*unaffected
LinuxLinux5.14.16 <= 5.14.*unaffected
LinuxLinux5.15 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

CVE Program Container

Additional References

References