Ubuntu 19.10 - ubuntu-aufs-modified mmap_region() Breaks Refcounting in overlayfs/shiftfs Error Path

Tested on 19.10. Ubuntu's aufs kernel patch includes the following change which I interestingly can't see in the AUFS code at https://github.com/sfjro/aufs5-linux/blob/master/mm/mmap.c: ================================================================== +define vmafputvma vmadofputvma, func, LINE...

UBUNTU-CVE-2019-15794

Overlayfs in the Linux kernel and shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, both replace vma-vmfile in their mmap handlers. On error the original value is not restored, and the reference is put for the file to which vmfile points. On...