reading /proc/$PID/environ returns Permission Denied

I am trying to export DBUS_SESSION_BUS_ADDRESS as environment variable in a startup script to change the background via gsettings. This script was working before a recent Ubuntu update. I am guessing that something changed in the 20.04.03 release, but after looking at the release notes I couldn't find anything relevant, so I am not sure.

Here is the relevant snippet of shell script code that I am using to attempt to export DBUS_SESSION_BUS_ADDRESS as an environment variable

pid_gnome=$(pgrep gnome-session | head -1)
DBUS_SESSION_BUS_ADDRESS=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/${pid_gnome}/environ|cut -d= -f2- | tr -d '\0\n')
export DBUS_SESSION_BUS_ADDRESS=${DBUS_SESSION_BUS_ADDRESS}

I get this error:

grep /proc/$PID/environ PERMISSION DENIED

If I manually try to cat /proc/$PID/environ, I also get permission denied. If I use sudo it works.

Did something change regarding the permissions for gnome-session environ recently?
If so, how can I export the DBUS_SESSION_BUS_ADDRESS as environment variable in a startup script ?

Thanks.

Edit: I have managed to get the script running again by setting the DISPLAY variable to DISPLAY=:1
I am confused as to why my DISPLAY is :1 and not :0, but no complaints here and that isn't the topic of the question.

My question still stands because I'm curious about how to export the DBUS_SESSION_BUS_ADDRESS as an environment variable, but it is not urgent or anything.