linux-kernel - [PATCH v2] xen/gntdev: Don't allocate struct gntdev_copy

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Date:	Fri, 15 Jan 2016 15:06:35 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	konrad.wilk@...cle.com, david.vrabel@...rix.com
Cc:	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH v2] xen/gntdev: Don't allocate struct gntdev_copy_batch on stack

struct gntdev_copy_batch is over 1300 bytes in size, we shouldn't
put it on stack.

Some compilers (e.g. 5.2.1) complain:
 drivers/xen/gntdev.c: In function ‘gntdev_ioctl_grant_copy.isra.5’:
 drivers/xen/gntdev.c:949:1: warning: the frame size of 1416 bytes
  is larger than 1024 bytes [-Wframe-larger-than=]

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
---
v2: Missed kfree on non-error path

 drivers/xen/gntdev.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index dc49538..6a5a6ef 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -915,15 +915,19 @@ static int gntdev_grant_copy_seg(struct gntdev_copy_batch *batch,
 static long gntdev_ioctl_grant_copy(struct gntdev_priv *priv, void __user *u)
 {
 	struct ioctl_gntdev_grant_copy copy;
-	struct gntdev_copy_batch batch;
+	struct gntdev_copy_batch *batch;
 	unsigned int i;
 	int ret = 0;
 
 	if (copy_from_user(&copy, u, sizeof(copy)))
 		return -EFAULT;
 
-	batch.nr_ops = 0;
-	batch.nr_pages = 0;
+	batch = kmalloc(sizeof(*batch), GFP_KERNEL);
+	if (!batch)
+		return -ENOMEM;
+
+	batch->nr_ops = 0;
+	batch->nr_pages = 0;
 
 	for (i = 0; i < copy.count; i++) {
 		struct gntdev_grant_copy_segment seg;
@@ -933,18 +937,22 @@ static long gntdev_ioctl_grant_copy(struct gntdev_priv *priv, void __user *u)
 			goto out;
 		}
 
-		ret = gntdev_grant_copy_seg(&batch, &seg, &copy.segments[i].status);
+		ret = gntdev_grant_copy_seg(batch, &seg,
+			&copy.segments[i].status);
 		if (ret < 0)
 			goto out;
 
 		cond_resched();
 	}
-	if (batch.nr_ops)
-		ret = gntdev_copy(&batch);
+	if (batch->nr_ops)
+		ret = gntdev_copy(batch);
+
+	kfree(batch);
 	return ret;
 
   out:
-	gntdev_put_pages(&batch);
+	gntdev_put_pages(batch);
+	kfree(batch);
 	return ret;
 }
 
-- 
2.5.0