linux-kernel - [PATCH v3] usb: gadget: ffs: Fix sparse error

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Message-ID: <1419422401-8401-1-git-send-email-rseelaboyina@nvidia.com>
Date:	Wed, 24 Dec 2014 17:30:01 +0530
From:	Rohith Seelaboyina <rseelaboyina@...dia.com>
To:	<balbi@...com>, <gregkh@...uxfoundation.org>, <mina86@...a86.com>,
	<r.baldyga@...sung.com>, <andrzej.p@...sung.com>
CC:	<joe@...ches.com>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Rohith Seelaboyina <rseelaboyina@...dia.com>
Subject: [PATCH v3] usb: gadget: ffs: Fix sparse error

This patch fixes the sparse error in functionfs
driver.

drivers/usb/gadget/function/f_fs.c:400:44: error: bad
constant experssion.

Dynamic memory allocation through kcalloc is more safer
than declaring variable array size, Fix this error by
using kcalloc for memory allocation, Check if memory
allocation is successful and return -ENOMEM on failure.

Signed-off-by: Rohith Seelaboyina <rseelaboyina@...dia.com>
---
Changes in v3:
   - Follow kernel coding style to seperate variable
     declaration and assignment.
Changes in v2:
   - Use kcalloc to allocate memory instead of using 
     kmalloc and memset.

 drivers/usb/gadget/function/f_fs.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 63314ede7ba6..8af3f7906c83 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -397,10 +397,13 @@ static ssize_t __ffs_ep0_read_events(struct ffs_data *ffs, char __user *buf,
 	 * We are holding ffs->ev.waitq.lock and ffs->mutex and we need
 	 * to release them.
 	 */
-	struct usb_functionfs_event events[n];
 	unsigned i = 0;
+	int ret;
+	struct usb_functionfs_event *events;
 
-	memset(events, 0, sizeof events);
+	events = kcalloc(n, sizeof(*events), GFP_KERNEL);
+	if (!events)
+		return -ENOMEM;
 
 	do {
 		events[i].type = ffs->ev.types[i];
@@ -421,8 +424,10 @@ static ssize_t __ffs_ep0_read_events(struct ffs_data *ffs, char __user *buf,
 	spin_unlock_irq(&ffs->ev.waitq.lock);
 	mutex_unlock(&ffs->mutex);
 
-	return unlikely(__copy_to_user(buf, events, sizeof events))
-		? -EFAULT : sizeof events;
+	ret = unlikely(__copy_to_user(buf, events, n * sizeof(*events)))
+		? -EFAULT : n * sizeof(*events);
+	kfree(events);
+	return ret;
 }
 
 static ssize_t ffs_ep0_read(struct file *file, char __user *buf,
-- 
1.9.1

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