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From:   Soenke Huster <soenke.huster@eknoes.de>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Soenke Huster <soenke.huster@eknoes.de>,
        linux-kernel@vger.kernel.org
Subject: [PATCH] driver core: fix null pointer deref in device_find_child
Date:   Thu, 20 Jan 2022 16:02:46 +0100
Message-Id: <20220120150246.6216-1-soenke.huster@eknoes.de>
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Similar to device_for_each_child, device_find_child should not ooops
if parent->p is NULL. While fuzzing the Bluetooth subsystem, I got a null
pointer dereference in next_device, which is prevented by this change.

Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=215497
Signed-off-by: Soenke Huster <soenke.huster@eknoes.de>
---
I found this while fuzzing the bluetooth subsystem and reported this bug
in bugzilla. As I feel more like a kernelnewbie, I am not sure whether
this needs to be patched in driver core, or is just an issue of the
bluetooth subsystem itself. If the latter is the case: sorry for the
spam!

A similar fix was applied in 014c90dbb9b6 ("driver core: prevent
device_for_each_child from oopsing") for device_for_each_child, which is
mentioned in the docstring of device_find_child as similar function.

 drivers/base/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 7bb957b11861..654d904631f9 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3780,7 +3780,7 @@ struct device *device_find_child(struct device *parent, void *data,
 	struct klist_iter i;
 	struct device *child;
 
-	if (!parent)
+	if (!parent || !parent->p)
 		return NULL;
 
 	klist_iter_init(&parent->p->klist_children, &i);
-- 
2.34.1