linux-kernel - [RESEND PATCH v2 2/2] serial: samsung: Fix possible out of bounds access on non-DT platform

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Date:	Thu, 16 Jun 2016 08:27:36 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	Kevin Hilman <khilman@...nel.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	arnd@...db.de, Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: [RESEND PATCH v2 2/2] serial: samsung: Fix possible out of bounds
 access on non-DT platform

On non-DeviceTree platforms, the index of serial device is a static
variable incremented on each probe.  It is incremented even if deferred
probe happens when getting the clock in s3c24xx_serial_init_port().

This index is used for referencing elements of statically allocated
s3c24xx_serial_ports array.  In case of re-probe, the index will point
outside of this array leading to memory corruption.

Increment the index only on successful probe.

Reported-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Fixes: b497549a035c ("[ARM] S3C24XX: Split serial driver into core and per-cpu drivers")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

---

Not cc-ing stable because:
1. It is just a possibility, not really reproduced (I don't have non-DT
   platform).
2. I am not sure whether deferred probe may happen on non-DT platform.

Changes since v1:
1. New patch.
---
 drivers/tty/serial/samsung.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index f0bd2ec0db59..4d2924f61e0b 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1844,8 +1844,6 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
 	ourport->min_dma_size = max_t(int, ourport->port.fifosize,
 				    dma_get_cache_alignment());
 
-	probe_index++;
-
 	dbg("%s: initialising port %p...\n", __func__, ourport);
 
 	ret = s3c24xx_serial_init_port(ourport, pdev);
@@ -1875,6 +1873,8 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
 	if (ret < 0)
 		dev_err(&pdev->dev, "failed to add cpufreq notifier\n");
 
+	probe_index++;
+
 	return 0;
 }
 
-- 
1.9.1