[Bug 90681] Radeon Kernel Oops & Lockup when switching on DisplayPort attached monitor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90681

            Bug ID: 90681
           Summary: Radeon Kernel Oops & Lockup when switching on
                    DisplayPort attached monitor
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: major
          Priority: medium
         Component: DRM/Radeon
          Assignee: dri-devel at lists.freedesktop.org
          Reporter: bradfirj at fstab.me

Created attachment 116079
  --> https://bugs.freedesktop.org/attachment.cgi?id=116079&action=edit
journalctl output for crash

Switching my DisplayPort attached monitor on (or off and then on again) while
booted to multiuser target (no Xorg or Wayland) causes a kernel Oops, followed
by soft-lockups which render the system unusable.

Doing the same while at the full Graphical target causes gnome-shell to crash,
but it is possible to recover the system by logging in again.

The kernel error and IP are:
>May 24 23:25:28 fedora-workstation.home kernel: BUG: unable to handle kernel NULL pointer dereference at 00000000000003b0
>May 24 23:25:28 fedora-workstation.home kernel: IP: [<ffffffffa0152055>] radeon_connector_edid+0x5/0x70 [radeon]

Full journal from a reproduction of the bug will be attached, as will lspci
-nn.

I have isolated this using git bisect to the following commit (the patch for
which is attached to this bug).
This is a commit currently part of the linux-stable tree and lies between 4.0.2
and 4.0.3

>016a255b7835ee7e49a3eba3c14ba0bc0221a4f8 is the first bad commit
>commit 016a255b7835ee7e49a3eba3c14ba0bc0221a4f8
>Author: Alex Deucher <alexander.deucher at amd.com>
>Date:   Tue Apr 7 09:52:42 2015 -0400
>
>    drm/radeon: only mark audio as connected if the monitor supports it (v3)
>    
>    commit 0f55db36d49d45b80eff0c0a2a498766016f458b upstream.
>    
>    Otherwise the driver may try and send audio which may confuse the
>    monitor.
>    
>    v2: set pin to NULL if no audio
>    v3: avoid crash with analog encoders
>    
>    Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
>    Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>>
>
>:040000 040000 de0366a6790f5c91d175bcb89cb34956bbe72b26 >bbdb5734961f824558152c7c34a840c78bc3a9a9 M	drivers

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