linux-kernel - [PATCH] gpio: null pointer dereference in error handling in gpiolib.c

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Message-ID: <52202948.7010303@sonymobile.com>
Date:	Thu, 29 Aug 2013 22:10:32 -0700
From:	Frank Rowand <frank.rowand@...ymobile.com>
To:	linus.walleij@...aro.org
CC:	grant.likely@...aro.org, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org, tim.bird@...ymobile.com
Subject: [PATCH] gpio: null pointer dereference in error handling in gpiolib.c


Avoid calling desc_to_gpio() if desc->chip is NULL, as this will
cause a kernel panic.

In the code above the calls, there is a test for !chip, which
comes to the 'fail' label if true. In this case, the code
panics, since desc_to_gpio() uses desc->chip to look up the
gpio number.

An RFC patch that explained the cause of one example of panic when
desc->chip is NULL and fixed that example
(http://lkml.indiana.edu/hypermail/linux/kernel/1308.3/01473.html)
was accepted.  This patch fixes the remaining locations which have
the same problem.

Signed-off-by: Frank Rowand <frank.rowand@...ymobile.com>

---
  drivers/gpio/gpiolib.c |   33 	24 +	9 -	0 !
  1 file changed, 24 insertions(+), 9 deletions(-)

Index: b/drivers/gpio/gpiolib.c
===================================================================
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1676,9 +1676,14 @@ lose:
  	return status;
  fail:
  	spin_unlock_irqrestore(&gpio_lock, flags);
-	if (status)
-		pr_debug("%s: gpio-%d status %d\n", __func__,
-			 desc_to_gpio(desc), status);
+	if (status) {
+		if (desc->chip) {
+			pr_debug("%s: gpio-%d status %d\n", __func__,
+				 desc_to_gpio(desc), status);
+		} else {
+			pr_debug("%s: gpio-?? status %d\n", __func__, status);
+		}
+	}
  	return status;
  }

@@ -1745,9 +1750,14 @@ lose:
  	return status;
  fail:
  	spin_unlock_irqrestore(&gpio_lock, flags);
-	if (status)
-		pr_debug("%s: gpio-%d status %d\n", __func__,
-			 desc_to_gpio(desc), status);
+	if (status) {
+		if (desc->chip) {
+			pr_debug("%s: gpio-%d status %d\n", __func__,
+				 desc_to_gpio(desc), status);
+		} else {
+			pr_debug("%s: gpio-?? status %d\n", __func__, status);
+		}
+	}
  	return status;
  }

@@ -1795,9 +1805,14 @@ static int gpiod_set_debounce(struct gpi

  fail:
  	spin_unlock_irqrestore(&gpio_lock, flags);
-	if (status)
-		pr_debug("%s: gpio-%d status %d\n", __func__,
-			 desc_to_gpio(desc), status);
+	if (status) {
+		if (desc->chip) {
+			pr_debug("%s: gpio-%d status %d\n", __func__,
+				 desc_to_gpio(desc), status);
+		} else {
+			pr_debug("%s: gpio-?? status %d\n", __func__, status);
+		}
+	}

  	return status;
  }
--
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