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This call changes an ingredient in the pathname resolution process
and does nothing else. In particular, it is not intended to be used
for any kind of security purpose, neither to fully sandbox a process
nor to restrict filesystem system calls. In the past, chroot() has
been used by daemons to restrict themselves prior to passing paths
supplied by untrusted users to system calls such as open(2).
However, if a folder is moved out of the chroot directory, an
attacker can exploit that to get out of the chroot directory as well.
The easiest way to do that is to chdir(2) to the to-be-moved
directory, wait for it to be moved out, then open a path like
../../../etc/passwd.
A slightly trickier variation also works under some circumstances if
chdir(2) is not permitted. If a daemon allows a "chroot directory"
to be specified, that usually means that if you want to prevent
remote users from accessing files outside the chroot directory, you
must ensure that folders are never moved out of it.
This call does not change the current working directory, so that
after the call '.' can be outside the tree rooted at '/'. In
particular, the superuser can escape from a "chroot jail" by doing:
mkdir foo; chroot foo; cd ..
This call does not close open file descriptors, and such file
descriptors may allow access to files outside the chroot tree.
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