So if you want the root access back on the latest android marshmallow then follow below guide to root android marshmallow.Thanks to XDA dev varun.chitre15 for Thunderzap kernel which make the Selinux permissive of android Marshmallow.
Unluckily if you didn’t got the OTA update of android marshmallow then follow below link to update it manually to android M 6.0
So for rooting your Micromax Canvas A1 Running on android Marshmallow you have to flash ThunderZAP kernel and the latest Super Su v2.50 that support android marshmallow 6.0
1.Must have custom recovery in your device (TWRP or CWM)
2.Download Thunder Zap Kernel.zip
3.Download SuperSu v2.50.zip(Supports marshmallow)
4.Do backup of your current ROM from recovery.
#How to root Micromax Canvas A1 running on Android M 6.0
1.Download Both Thuderzap kernel.zip and Super su v2.50.zip and place it in your device memory.
2.Then reboot your device into recovery mode.
3.Tap on “Install” in recovery mode and the select ThuderZap.zip from your memory where you pasted it in 1st step.
4.Now After selecting the .zip file do “Swipe to confirm flash” at the bottom of the screen.
5.Now back to home in TWRP recovery and Flash the latest Super Su v2.50 similarly as you flashed the Thunder Zap kernel in step 3 and Step 4.
6.Once Flashed both the files in sequence reboot our device.
Done! You Successfully Rooted Micromax canvas A1 running on android marshmallow 6.0