[dpdk-stable] patch 'igb_uio: fix refcount if open returns error' has been queued to stable release 18.08.1

[Kevin Traynor]

Hi,

FYI, your patch has been queued to stable release 18.08.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 11/27/18. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the patch applied
to the branch. If the code is different (ie: not only metadata diffs), due for example to
a change in context or macro names, please double check it.

Thanks.

Kevin Traynor

---
>From 4fa9cde4881ec5327bcb44a6a9ff36a29d18b621 Mon Sep 17 00:00:00 2001
From: Stephen Hemminger <stephen at networkplumber.org>
Date: Fri, 14 Sep 2018 08:30:19 -0700
Subject: [PATCH] igb_uio: fix refcount if open returns error

[ upstream commit ab856f2947ef0af523eb4d22f4aa8347bbf07391 ]

This fixes the problem of reference count leak if
igbuio_pci_enable_interrupts fails.

Also, replace mutex and integer with a kernel atomic counter.
This is standard pattern for kernel devices.

Fixes: 19685d5aa79c ("igb_uio: allow multi-process access")

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
Acked-by: Ferruh Yigit <ferruh.yigit at intel.com>
---
 kernel/linux/igb_uio/igb_uio.c | 33 +++++++++++----------------------
 1 file changed, 11 insertions(+), 22 deletions(-)

diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
index 3398eacd3..fede66cf2 100644
--- a/kernel/linux/igb_uio/igb_uio.c
+++ b/kernel/linux/igb_uio/igb_uio.c
@@ -27,6 +27,5 @@ struct rte_uio_pci_dev {
 	struct pci_dev *pdev;
 	enum rte_intr_mode mode;
-	struct mutex lock;
-	int refcnt;
+	atomic_t refcnt;
 };
 
@@ -321,9 +320,6 @@ igbuio_pci_open(struct uio_info *info, struct inode *inode)
 	int err;
 
-	mutex_lock(&udev->lock);
-	if (++udev->refcnt > 1) {
-		mutex_unlock(&udev->lock);
+	if (atomic_inc_return(&udev->refcnt) != 1)
 		return 0;
-	}
 
 	/* set bus master, which was cleared by the reset function */
@@ -332,10 +328,9 @@ igbuio_pci_open(struct uio_info *info, struct inode *inode)
 	/* enable interrupts */
 	err = igbuio_pci_enable_interrupts(udev);
-	mutex_unlock(&udev->lock);
 	if (err) {
+		atomic_dec(&udev->refcnt);
 		dev_err(&dev->dev, "Enable interrupt fails\n");
-		return err;
 	}
-	return 0;
+	return err;
 }
 
@@ -346,17 +341,12 @@ igbuio_pci_release(struct uio_info *info, struct inode *inode)
 	struct pci_dev *dev = udev->pdev;
 
-	mutex_lock(&udev->lock);
-	if (--udev->refcnt > 0) {
-		mutex_unlock(&udev->lock);
-		return 0;
+	if (atomic_dec_and_test(&udev->refcnt)) {
+		/* disable interrupts */
+		igbuio_pci_disable_interrupts(udev);
+
+		/* stop the device from further DMA */
+		pci_clear_master(dev);
 	}
 
-	/* disable interrupts */
-	igbuio_pci_disable_interrupts(udev);
-
-	/* stop the device from further DMA */
-	pci_clear_master(dev);
-
-	mutex_unlock(&udev->lock);
 	return 0;
 }
@@ -490,5 +480,4 @@ igbuio_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 		return -ENOMEM;
 
-	mutex_init(&udev->lock);
 	/*
 	 * enable device: ask low-level code to enable I/O and
@@ -530,4 +519,5 @@ igbuio_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	udev->info.priv = udev;
 	udev->pdev = dev;
+	atomic_set(&udev->refcnt, 0);
 
 	err = sysfs_create_group(&dev->dev.kobj, &dev_attr_grp);
@@ -581,5 +571,4 @@ igbuio_pci_remove(struct pci_dev *dev)
 	struct rte_uio_pci_dev *udev = pci_get_drvdata(dev);
 
-	mutex_destroy(&udev->lock);
 	sysfs_remove_group(&dev->dev.kobj, &dev_attr_grp);
 	uio_unregister_device(&udev->info);
-- 
2.19.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2018-11-21 16:44:31.308435521 +0000
+++ 0014-igb_uio-fix-refcount-if-open-returns-error.patch	2018-11-21 16:44:30.000000000 +0000
@@ -1,8 +1,10 @@
-From ab856f2947ef0af523eb4d22f4aa8347bbf07391 Mon Sep 17 00:00:00 2001
+From 4fa9cde4881ec5327bcb44a6a9ff36a29d18b621 Mon Sep 17 00:00:00 2001
 From: Stephen Hemminger <stephen at networkplumber.org>
 Date: Fri, 14 Sep 2018 08:30:19 -0700
 Subject: [PATCH] igb_uio: fix refcount if open returns error
 
+[ upstream commit ab856f2947ef0af523eb4d22f4aa8347bbf07391 ]
+
 This fixes the problem of reference count leak if
 igbuio_pci_enable_interrupts fails.
 
@@ -10,7 +12,6 @@
 This is standard pattern for kernel devices.
 
 Fixes: 19685d5aa79c ("igb_uio: allow multi-process access")
-Cc: stable at dpdk.org
 
 Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
 Acked-by: Ferruh Yigit <ferruh.yigit at intel.com>