linux-kernel - [PATCH 4.13 26/28] staging: greybus: spilib: fix use-after-free after deregistration

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Date:   Sun, 19 Nov 2017 15:44:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        Viresh Kumar <viresh.kumar@...aro.org>
Subject: [PATCH 4.13 26/28] staging: greybus: spilib: fix use-after-free after deregistration

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@...nel.org>

commit 770b03c2ca4aa44d226cf248f86aa23e546147d0 upstream.

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")
Signed-off-by: Johan Hovold <johan@...nel.org>
Reviewed-by: Rui Miguel Silva <rmfrfs@...il.com>
Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/greybus/spilib.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/staging/greybus/spilib.c
+++ b/drivers/staging/greybus/spilib.c
@@ -544,12 +544,15 @@ int gb_spilib_master_init(struct gb_conn
 
 	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_con
 	struct spi_master *master = gb_connection_get_data(connection);
 
 	spi_unregister_master(master);
-	spi_master_put(master);
 }
 EXPORT_SYMBOL_GPL(gb_spilib_master_exit);