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drm/vc4: kms: Clear the HVS FIFO commit pointer once done

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commit d134c5ff71c7f2320fc7997f2fbbdedf0c76889a upstream.

Commit 9ec03d7f1ed3 ("drm/vc4: kms: Wait on previous FIFO users before a
commit") introduced a wait on the previous commit done on a given HVS
FIFO.

However, we never cleared that pointer once done. Since
drm_crtc_commit_put can free the drm_crtc_commit structure directly if
we were the last user, this means that it can lead to a use-after free
if we were to duplicate the state, and that stale pointer would even be
copied to the new state.

Set the pointer to NULL once we're done with the wait so that we don't
carry over a pointer to a free'd structure.

Fixes: 9ec03d7f1ed3 ("drm/vc4: kms: Wait on previous FIFO users before a commit")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Tested-by: Jian-Hong Pan <jhp@endlessos.org>
Link: https://lore.kernel.org/r/20211117094527.146275-5-maxime@cerno.tech
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Maxime Ripard 2021-11-17 10:45:25 +01:00 committed by Greg Kroah-Hartman
parent 53f9601e90
commit 2931db9a5e
1 changed files with 1 additions and 0 deletions
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1
drivers/gpu/drm/vc4/vc4_kms.c
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@ -379,6 +379,7 @@ static void vc4_atomic_commit_tail(struct drm_atomic_state *state)
drm_err(dev, "Timed out waiting for commit\n");
drm_crtc_commit_put(commit);
old_hvs_state->fifo_state[channel].pending_commit = NULL;
}
if (vc4->hvs->hvs5)