linux-kernel - [PATCH] staging: greybus: spilib: fix use-after-free after deregistration

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Message-Id: <20171029120133.32585-1-johan@kernel.org>
Date:   Sun, 29 Oct 2017 13:01:33 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Rui Miguel Silva <rmfrfs@...il.com>,
        Viresh Kumar <vireshk@...nel.org>
Cc:     Johan Hovold <johan@...nel.org>, Alex Elder <elder@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        greybus-dev@...ts.linaro.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>
Subject: [PATCH] staging: greybus: spilib: fix use-after-free after deregistration

Remove erroneous spi_master_put() after controller deregistration which
would access the already freed spi controller.

Note that spi_unregister_master() drops our only controller reference.

Fixes: ba3e67001b42 ("greybus: SPI: convert to a gpbridge driver")
Cc: stable <stable@...r.kernel.org>     # 4.9
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/staging/greybus/spilib.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/greybus/spilib.c b/drivers/staging/greybus/spilib.c
index e97b19148497..1e7321a1404c 100644
--- a/drivers/staging/greybus/spilib.c
+++ b/drivers/staging/greybus/spilib.c
@@ -544,11 +544,14 @@ int gb_spilib_master_init(struct gb_connection *connection, struct device *dev,
 
 	return 0;
 
-exit_spi_unregister:
-	spi_unregister_master(master);
 exit_spi_put:
 	spi_master_put(master);
 
+	return ret;
+
+exit_spi_unregister:
+	spi_unregister_master(master);
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(gb_spilib_master_init);
@@ -558,7 +561,6 @@ void gb_spilib_master_exit(struct gb_connection *connection)
 	struct spi_master *master = gb_connection_get_data(connection);
 
 	spi_unregister_master(master);
-	spi_master_put(master);
 }
 EXPORT_SYMBOL_GPL(gb_spilib_master_exit);
 
-- 
2.14.3