btrfs: simplify kmalloc+copy_from_user to memdup_user

Use memdup_user rather than duplicating its implementation
This is a little bit restricted to reduce false positives

The semantic patch that makes this report is available
in scripts/coccinelle/api/memdup_user.cocci.

More information about semantic patching is available at
http://coccinelle.lip6.fr/

Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 08ac53c5f78d7402bed71fbd25f99a31d55f5082..864aab4b1bfa77ff95eb9c83d7584e6e4b6ed95f 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2715,15 +2715,10 @@ static long btrfs_ioctl_file_extent_same(struct file *file,
        size = sizeof(tmp) +
                tmp.dest_count * sizeof(struct btrfs_ioctl_same_extent_info);
 
-       same = kmalloc(size, GFP_NOFS);
-       if (!same) {
-               ret = -EFAULT;
-               goto out;
-       }
+       same = memdup_user((struct btrfs_ioctl_same_args __user *)argp, size);
 
-       if (copy_from_user(same,
-                          (struct btrfs_ioctl_same_args __user *)argp, size)) {
-               ret = -EFAULT;
+       if (IS_ERR(same)) {
+               ret = PTR_ERR(same);
                goto out;
        }