/etc/sysctl.d/10-zeropage.conf is in procps 2:3.3.10-4ubuntu2.4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | # Protect the zero page of memory from userspace mmap to prevent kernel
# NULL-dereference attacks against potential future kernel security
# vulnerabilities. (Added in kernel 2.6.23.)
#
# While this default is built into the Ubuntu kernel, there is no way to
# restore the kernel default if the value is changed during runtime; for
# example via package removal (e.g. wine, dosemu). Therefore, this value
# is reset to the secure default each time the sysctl values are loaded.
vm.mmap_min_addr = 65536
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