linux-kernel - [PATCH] tile-srom: avoid krealloc(... __GFP

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Date:	Thu, 28 Jul 2016 15:07:04 -0400
From:	Chris Metcalf <cmetcalf@...lanox.com>
To:	Joe Perches <joe@...ches.com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Arnd Bergmann <arnd@...db.de>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	Ferruh Yigit <fery@...ress.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:	Chris Metcalf <cmetcalf@...lanox.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] tile-srom: avoid krealloc(... __GFP_ZERO) pattern

Joe Perches points out [1] that this pattern isn't currently safe.
This driver doesn't really need the zeroing semantic anyway;
by restructuring the code slightly we can initialize all the
fields of the structure up front instead.

[1] https://lkml.kernel.org/r/1469729491.3998.58.camel@perches.com

Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>
---
 drivers/char/tile-srom.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/char/tile-srom.c b/drivers/char/tile-srom.c
index 69f6b4acc377..398800edb2cc 100644
--- a/drivers/char/tile-srom.c
+++ b/drivers/char/tile-srom.c
@@ -331,13 +331,11 @@ static const struct file_operations srom_fops = {
 /**
  * srom_setup_minor() - Initialize per-minor information.
  * @srom: Per-device SROM state.
- * @index: Device to set up.
+ * @devhdl: Partition device handle.
  */
-static int srom_setup_minor(struct srom_dev *srom, int index)
+static int srom_setup_minor(struct srom_dev *srom, int devhdl)
 {
-	struct device *dev;
-	int devhdl = srom->hv_devhdl;
-
+	srom->hv_devhdl = devhdl;
 	mutex_init(&srom->lock);
 
 	if (_srom_read(devhdl, &srom->total_size,
@@ -350,9 +348,7 @@ static int srom_setup_minor(struct srom_dev *srom, int index)
 		       SROM_PAGE_SIZE_OFF, sizeof(srom->page_size)) < 0)
 		return -EIO;
 
-	dev = device_create(srom_class, &srom_parent->dev,
-			    MKDEV(srom_major, index), srom, "%d", index);
-	return PTR_ERR_OR_ZERO(dev);
+	return 0;
 }
 
 /** srom_init() - Initialize the driver's module. */
@@ -365,7 +361,7 @@ static int srom_init(void)
 	 * Start with a plausible number of partitions; the krealloc() call
 	 * below will yield about log(srom_devs) additional allocations.
 	 */
-	srom_devices = kzalloc(4 * sizeof(struct srom_dev), GFP_KERNEL);
+	srom_devices = kmalloc(4 * sizeof(struct srom_dev), GFP_KERNEL);
 
 	/* Discover the number of srom partitions. */
 	for (i = 0; ; i++) {
@@ -373,7 +369,7 @@ static int srom_init(void)
 		char buf[20];
 		struct srom_dev *new_srom_devices =
 			krealloc(srom_devices, (i+1) * sizeof(struct srom_dev),
-				 GFP_KERNEL | __GFP_ZERO);
+				 GFP_KERNEL);
 		if (!new_srom_devices) {
 			result = -ENOMEM;
 			goto fail_mem;
@@ -387,7 +383,9 @@ static int srom_init(void)
 					  i, devhdl);
 			break;
 		}
-		srom_devices[i].hv_devhdl = devhdl;
+		result = srom_setup_minor(&srom_devices[i], devhdl);
+		if (result != 0)
+			goto fail_mem;
 	}
 	srom_devs = i;
 
@@ -431,9 +429,13 @@ static int srom_init(void)
 	srom_class->dev_groups = srom_dev_groups;
 	srom_class->devnode = srom_devnode;
 
-	/* Do per-partition initialization */
+	/* Create per-partition devices */
 	for (i = 0; i < srom_devs; i++) {
-		result = srom_setup_minor(srom_devices + i, i);
+		struct device *dev =
+			device_create(srom_class, &srom_parent->dev,
+				      MKDEV(srom_major, i), srom_devices + i,
+				      "%d", i);
+		result = PTR_ERR_OR_ZERO(dev);
 		if (result < 0)
 			goto fail_class;
 	}
-- 
2.7.2