linux-kernel - [PATCH 4.4 117/312] serial: samsung: Fix possible out of bounds access on non-DT platform

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Message-Id: <20200508123132.697716151@linuxfoundation.org>
Date:   Fri,  8 May 2020 14:31:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Krzysztof Kozlowski <k.kozlowski@...sung.com>
Subject: [PATCH 4.4 117/312] serial: samsung: Fix possible out of bounds access on non-DT platform

From: Krzysztof Kozlowski <k.kozlowski@...sung.com>

commit 926b7b5122c96e1f18cd20e85a286c7ec8d18c97 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/tty/serial/samsung.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1841,8 +1841,6 @@ static int s3c24xx_serial_probe(struct p
 	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);
@@ -1872,6 +1870,8 @@ static int s3c24xx_serial_probe(struct p
 	if (ret < 0)
 		dev_err(&pdev->dev, "failed to add cpufreq notifier\n");
 
+	probe_index++;
+
 	return 0;
 }