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.

Affected: Ubuntu:16.04:LTS: linux-gcp

Mohamed Ghannam discovered that a use-after-free vulnerability existed in the Netlink subsystem (XFRM) in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2017-16939)

It was discovered that the Linux kernel did not properly handle copy-on- write of transparent huge pages. A local attacker could use this to cause a denial of service (application crashes) or possibly gain administrative privileges. (CVE-2017-1000405)

Fan Wu, Haoran Qiu, and Shixiong Zhao discovered that the associative array implementation in the Linux kernel sometimes did not properly handle adding a new entry. A local attacker could use this to cause a denial of service (system crash). (CVE-2017-12193)

Eric Biggers discovered that the key management subsystem in the Linux kernel did not properly restrict adding a key that already exists but is uninstantiated. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2017-15299)

It was discovered that a null pointer dereference error existed in the PowerPC KVM implementation in the Linux kernel. A local attacker could use this to cause a denial of service (system crash). (CVE-2017-15306)

Eric Biggers discovered a race condition in the key management subsystem of the Linux kernel around keys in a negative state. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitr…