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From:   Dinghao Liu <dinghao.liu@zju.edu.cn>
To:     dinghao.liu@zju.edu.cn
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>,
        Michal Wilczynski <michal.wilczynski@intel.com>,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] ACPI: video: Fix a null-pointer-dereference in acpi_video_bus_add
Date:   Mon, 25 Sep 2023 16:08:44 +0800
Message-Id: <20230925080844.32699-1-dinghao.liu@zju.edu.cn>
Precedence: bulk

acpi_video_bus_add_notify_handler() could free video->input and
set it to NULL on failure, but this failure will be missed in its
caller acpi_video_bus_add(). As a result, when an error happens in
acpi_dev_install_notify_handler(), acpi_video_bus_add() will call
acpi_video_bus_remove_notify_handler(), where a potential null pointer
video->input is dereferenced in input_unregister_device().

Fix this by adding a return value check and adjusting the following
error handling code.

Fixes: 6f7016819766 ("ACPI: video: Install Notify() handler directly")
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
---
 drivers/acpi/acpi_video.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 948e31f7ce6e..b411948594ff 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -2057,7 +2057,9 @@ static int acpi_video_bus_add(struct acpi_device *device)
 	    !auto_detect)
 		acpi_video_bus_register_backlight(video);
 
-	acpi_video_bus_add_notify_handler(video);
+	error = acpi_video_bus_add_notify_handler(video);
+	if (error)
+		goto err_del;
 
 	error = acpi_dev_install_notify_handler(device, ACPI_DEVICE_NOTIFY,
 						acpi_video_bus_notify);
@@ -2067,10 +2069,11 @@ static int acpi_video_bus_add(struct acpi_device *device)
 	return 0;
 
 err_remove:
+	acpi_video_bus_remove_notify_handler(video);
+err_del:
 	mutex_lock(&video_list_lock);
 	list_del(&video->entry);
 	mutex_unlock(&video_list_lock);
-	acpi_video_bus_remove_notify_handler(video);
 	acpi_video_bus_unregister_backlight(video);
 err_put_video:
 	acpi_video_bus_put_devices(video);
-- 
2.17.1