CVE-2019-15794 Reference counting error in overlayfs/shiftfs error path when used in conjuction with aufs

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...