Rooted but su says "Permission denied"

Question

I have this "old" Lenovo A2107 tablet which I rooted years ago (using a download from http://androidforums.com/threads/a2107-root-mods-and-rom-discussion.661261/, tho running its root.bat script by hand from my GNU/Linux machine) and that worked fine.

Then I passed this tablet to my daughter for a couple years, and now I got it back.

/system/bin/su is still present, still the same date and size, still mode "rwsr-sr-x", still the same firmware (Android 4.0.3) so all looks fine, but when I try to run it from a shell, it just tells me "Permission denied".

Any idea what might be going on? What I could try to do to track it down?

Answer 1

Nowadays Magisk is commonly used for rooting.

I've found that on my Oneplus 5 (Oxygen OS, Nougat) it was sufficient to go to Magisk Manager app, open superuser permissions screen and toggle Shell (com.android.shell) to resolve the adb su permission denied problem.

Answer 2

FWIW... I had a similar problem ( running 'su' from ADB shell yielded 'permission denied' ), so I'll describe my solution.

For context, I had rebrained my Galaxy Nexus with CyanogenMod.

So, I looked at the system settings, and it contains a 'Superuser' section; in that section's own settings ( small menu ), there is a 'Superuser Access' option, which was set to 'Apps only'. I changed that to 'Apps and ADB', and then I was able to start an ADB shell, and from that shell, I was now allowed to run 'su'. :-)