After upgrading do the Kernel 4.18, a chroot I used somewhat frequently stopped working. Everytime I tried to start it I just got that simple, but horrifying message:

~# chroot /path/to/jail /bin/bash -i -l
Segmentation Fault

As the project I was working on did not depended on that chroot I’ve set this aside until now.

It turns out that LEGACY_VSYSCALL emulation was disabled by the Debian new Kernels…

~# diff /boot/config-4.9.0-8-amd64 /boot/config-4.18.0-0.bpo.1-amd64 | grep VSYSCALL
 CONFIG_X86_VSYSCALL_EMULATION=y
-# CONFIG_LEGACY_VSYSCALL_NATIVE is not set
-CONFIG_LEGACY_VSYSCALL_EMULATE=y
-# CONFIG_LEGACY_VSYSCALL_NONE is not set
+# CONFIG_LEGACY_VSYSCALL_EMULATE is not set
+CONFIG_LEGACY_VSYSCALL_NONE=y

Luckily this can be changed in the kernel command line, so adding vsyscall=emulate in the Grub command line configuration made it work.

So to solve the problem I njsut had to change the file /etc/default/grub so it contained a line such as:

...
GRUB_CMDLINE_LINUX_DEFAULT="quiet vsyscall=emulate"
...

Call update-grub and reboot!

Why?

Looks like this changes are related to the ASLR (Address Space Layout Randomization) security feature and enabling this emulation can lead to security vulnerabilities.

Sources

* This was the post I found that helped me solve this problem: https://github.com/moby/moby/issues/28705