shared: util.c: fix buffer overflow in alias_normalize()

shared: util.c: fix buffer overflow in alias_normalize()

The while-loop inside the '[' case of alias_normalize() increments the
index 'i' without checking against PATH_MAX bounds. If the input string
contains an opening '[' followed by many characters without a closing ']',
the index can exceed PATH_MAX-1, causing a buffer overflow when writing
to buf[i].

Signed-off-by: Anton Moryakov <ant.v.moryakov@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/431
Signed-off-by: Lucas De Marchi <demarchi@kernel.org>