Vulnerability Description
The Linux Kernel versions 2.6.38 through 4.14 have a problematic use of pmd_mkdirty() in the touch_pmd() function inside the THP implementation. touch_pmd() can be reached by get_user_pages(). In such case, the pmd will become dirty. This scenario breaks the new can_follow_write_pmd()'s logic - pmd can become dirty without going through a COW cycle. This bug is not as severe as the original "Dirty cow" because an ext4 file (or any other regular file) cannot be mapped using THP. Nevertheless, it does allow us to overwrite read-only huge pages. For example, the zero huge page and sealed shmem files can be overwritten (since their mapping can be populated using THP). Note that after the first write page-fault to the zero page, it will be replaced with a new fresh (and zeroed) thp.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Linux | Linux Kernel | >= 3.2.87, < 3.3 |
Related Weaknesses (CWE)
References
- http://www.securityfocus.com/bid/102032Third Party AdvisoryVDB Entry
- http://www.securitytracker.com/id/1040020Third Party AdvisoryVDB Entry
- https://access.redhat.com/errata/RHSA-2018:0180Third Party Advisory
- https://medium.com/bindecy/huge-dirty-cow-cve-2017-1000405-110eca132de0ExploitIssue TrackingThird Party Advisory
- https://source.android.com/security/bulletin/pixel/2018-02-01Third Party Advisory
- https://www.exploit-db.com/exploits/43199/ExploitIssue TrackingThird Party Advisory
- http://www.securityfocus.com/bid/102032Third Party AdvisoryVDB Entry
- http://www.securitytracker.com/id/1040020Third Party AdvisoryVDB Entry
- https://access.redhat.com/errata/RHSA-2018:0180Third Party Advisory
- https://medium.com/bindecy/huge-dirty-cow-cve-2017-1000405-110eca132de0ExploitIssue TrackingThird Party Advisory
- https://source.android.com/security/bulletin/pixel/2018-02-01Third Party Advisory
- https://www.exploit-db.com/exploits/43199/ExploitIssue TrackingThird Party Advisory
FAQ
What is CVE-2017-1000405?
CVE-2017-1000405 is a vulnerability with a CVSS score of 7.0 (HIGH). The Linux Kernel versions 2.6.38 through 4.14 have a problematic use of pmd_mkdirty() in the touch_pmd() function inside the THP implementation. touch_pmd() can be reached by get_user_pages(). In such...
How severe is CVE-2017-1000405?
CVE-2017-1000405 has been rated HIGH with a CVSS base score of 7.0/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2017-1000405?
Check the references section above for vendor advisories and patch information. Affected products include: Linux Linux Kernel.