linux-kernel - [PATCH 4.19 099/211] media: cec-notifier: clear cec_adap in cec_notifier

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Date:   Thu,  3 Oct 2019 17:52:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 099/211] media: cec-notifier: clear cec_adap in cec_notifier_unregister

From: Hans Verkuil <hverkuil-cisco@...all.nl>

[ Upstream commit 14d5511691e5290103bc480998bc322e68f139d4 ]

If cec_notifier_cec_adap_unregister() is called before
cec_unregister_adapter() then everything is OK (and this is the
case today). But if it is the other way around, then
cec_notifier_unregister() is called first, and that doesn't
set n->cec_adap to NULL.

So if e.g. cec_notifier_set_phys_addr() is called after
cec_notifier_unregister() but before cec_unregister_adapter()
then n->cec_adap points to an unregistered and likely deleted
cec adapter. So just set n->cec_adap->notifier and n->cec_adap
to NULL for rubustness.

Eventually cec_notifier_unregister will disappear and this will
be simplified substantially.

Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/cec/cec-notifier.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/cec/cec-notifier.c b/drivers/media/cec/cec-notifier.c
index dd2078b27a419..2424680f71c3d 100644
--- a/drivers/media/cec/cec-notifier.c
+++ b/drivers/media/cec/cec-notifier.c
@@ -123,6 +123,8 @@ void cec_notifier_unregister(struct cec_notifier *n)
 {
 	mutex_lock(&n->lock);
 	n->callback = NULL;
+	n->cec_adap->notifier = NULL;
+	n->cec_adap = NULL;
 	mutex_unlock(&n->lock);
 	cec_notifier_put(n);
 }
-- 
2.20.1