linux-kernel - [PATCH 11/29] drivers, media: convert cx88_core.refcount from atomic_t to refcount

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Date:   Mon,  6 Mar 2017 16:20:58 +0200
From:   Elena Reshetova <elena.reshetova@...el.com>
To:     gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        netdev@...r.kernel.org, linux1394-devel@...ts.sourceforge.net,
        linux-bcache@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-media@...r.kernel.org, devel@...uxdriverproject.org,
        linux-pci@...r.kernel.org, linux-s390@...r.kernel.org,
        fcoe-devel@...n-fcoe.org, linux-scsi@...r.kernel.org,
        open-iscsi@...glegroups.com, devel@...verdev.osuosl.org,
        target-devel@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-usb@...r.kernel.org, peterz@...radead.org,
        Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        Kees Cook <keescook@...omium.org>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 11/29] drivers, media: convert cx88_core.refcount from atomic_t to refcount_t

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: David Windsor <dwindsor@...il.com>
---
 drivers/media/pci/cx88/cx88-cards.c | 2 +-
 drivers/media/pci/cx88/cx88-core.c  | 4 ++--
 drivers/media/pci/cx88/cx88.h       | 3 ++-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/media/pci/cx88/cx88-cards.c b/drivers/media/pci/cx88/cx88-cards.c
index cdfbde2..7fc5f5f 100644
--- a/drivers/media/pci/cx88/cx88-cards.c
+++ b/drivers/media/pci/cx88/cx88-cards.c
@@ -3670,7 +3670,7 @@ struct cx88_core *cx88_core_create(struct pci_dev *pci, int nr)
 	if (!core)
 		return NULL;
 
-	atomic_inc(&core->refcount);
+	refcount_set(&core->refcount, 1);
 	core->pci_bus  = pci->bus->number;
 	core->pci_slot = PCI_SLOT(pci->devfn);
 	core->pci_irqmask = PCI_INT_RISC_RD_BERRINT | PCI_INT_RISC_WR_BERRINT |
diff --git a/drivers/media/pci/cx88/cx88-core.c b/drivers/media/pci/cx88/cx88-core.c
index 973a9cd4..8bfa5b7 100644
--- a/drivers/media/pci/cx88/cx88-core.c
+++ b/drivers/media/pci/cx88/cx88-core.c
@@ -1052,7 +1052,7 @@ struct cx88_core *cx88_core_get(struct pci_dev *pci)
 			mutex_unlock(&devlist);
 			return NULL;
 		}
-		atomic_inc(&core->refcount);
+		refcount_inc(&core->refcount);
 		mutex_unlock(&devlist);
 		return core;
 	}
@@ -1073,7 +1073,7 @@ void cx88_core_put(struct cx88_core *core, struct pci_dev *pci)
 	release_mem_region(pci_resource_start(pci, 0),
 			   pci_resource_len(pci, 0));
 
-	if (!atomic_dec_and_test(&core->refcount))
+	if (!refcount_dec_and_test(&core->refcount))
 		return;
 
 	mutex_lock(&devlist);
diff --git a/drivers/media/pci/cx88/cx88.h b/drivers/media/pci/cx88/cx88.h
index 115414c..16c1313 100644
--- a/drivers/media/pci/cx88/cx88.h
+++ b/drivers/media/pci/cx88/cx88.h
@@ -24,6 +24,7 @@
 #include <linux/i2c-algo-bit.h>
 #include <linux/videodev2.h>
 #include <linux/kdev_t.h>
+#include <linux/refcount.h>
 
 #include <media/v4l2-device.h>
 #include <media/v4l2-fh.h>
@@ -339,7 +340,7 @@ struct cx8802_dev;
 
 struct cx88_core {
 	struct list_head           devlist;
-	atomic_t                   refcount;
+	refcount_t                   refcount;
 
 	/* board name */
 	int                        nr;
-- 
2.7.4