linux-kernel - re: drm: Add helpers to kick off self refresh mode in drivers

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Message-ID: <42c3d0e4-ee7a-2da8-a697-634a2717f688@canonical.com>
Date:   Fri, 14 Jun 2019 15:17:01 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Sean Paul <seanpaul@...omium.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        dri-devel@...ts.freedesktop.org
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: re: drm: Add helpers to kick off self refresh mode in drivers

Hi,

Static analysis with Coverity has picked up two potential issues with
the commit in linux-next:

commit 1452c25b0e60278820f3d2155c65f1bfcce5ee79
Author: Sean Paul <seanpaul@...omium.org>
Date:   Wed Jun 12 10:50:19 2019 -0400

    drm: Add helpers to kick off self refresh mode in drivers

1. There is a potential null dereference on the following code path in
function drm_self_refresh_helper_entry_work:

        state = drm_atomic_state_alloc(dev);
        if (!state) {
                ret = -ENOMEM;
                goto out;
        }

..the exit path out calls drm_atomic_state_put(state) which dereferences
the null state.

2. The following error exit path to out in function
drm_self_refresh_helper_entry_work will check if ret is -EDEADLK however
ret has not been initialized at this point:

       if (!crtc_state->enable)
                goto out;

       ...

out:
       if (ret == -EDEADLK) {
            ...
       }

Colin