linux-kernel - [PATCH 11/27] drivers/i2c: Use memdup

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Date:	Sat, 22 May 2010 10:21:45 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	"Jean Delvare (PC drivers, core)" <khali@...ux-fr.org>,
	"Ben Dooks (em, bedded platforms)" <ben-linux@...ff.org>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH 11/27] drivers/i2c: Use memdup_user

From: Julia Lawall <julia@...u.dk>

Use memdup_user when user data is immediately copied into the allocated
region.  Note that in the second case, the ++i is no longer necessary, as
the last value is already freed if needed by the call to memdup_user.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression from,to,size,flag;
position p;
identifier l1,l2;
@@

-  to = \(kmalloc@p\|kzalloc@p\)(size,flag);
+  to = memdup_user(from,size);
   if (
-      to==NULL
+      IS_ERR(to)
                 || ...) {
   <+... when != goto l1;
-  -ENOMEM
+  PTR_ERR(to)
   ...+>
   }
-  if (copy_from_user(to, from, size) != 0) {
-    <+... when != goto l2;
-    -EFAULT
-    ...+>
-  }
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>

---
 drivers/i2c/i2c-dev.c |   22 ++++++----------------
 1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index e0694e4..03e9ef8 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -167,13 +167,9 @@ static ssize_t i2cdev_write(struct file *file, const char __user *buf,
 	if (count > 8192)
 		count = 8192;
 
-	tmp = kmalloc(count, GFP_KERNEL);
-	if (tmp == NULL)
-		return -ENOMEM;
-	if (copy_from_user(tmp, buf, count)) {
-		kfree(tmp);
-		return -EFAULT;
-	}
+	tmp = memdup_user(buf, count);
+	if (IS_ERR(tmp))
+		return PTR_ERR(tmp);
 
 	pr_debug("i2c-dev: i2c-%d writing %zu bytes.\n",
 		iminor(file->f_path.dentry->d_inode), count);
@@ -247,15 +243,9 @@ static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,
 			break;
 		}
 		data_ptrs[i] = (u8 __user *)rdwr_pa[i].buf;
-		rdwr_pa[i].buf = kmalloc(rdwr_pa[i].len, GFP_KERNEL);
-		if (rdwr_pa[i].buf == NULL) {
-			res = -ENOMEM;
-			break;
-		}
-		if (copy_from_user(rdwr_pa[i].buf, data_ptrs[i],
-				   rdwr_pa[i].len)) {
-				++i; /* Needs to be kfreed too */
-				res = -EFAULT;
+		rdwr_pa[i].buf = memdup_user(data_ptrs[i], rdwr_pa[i].len);
+		if (IS_ERR(rdwr_pa[i].buf)) {
+			res = PTR_ERR(rdwr_pa[i].buf);
 			break;
 		}
 	}
--
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