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

Elena Reshetova
2017-03-06T14:20:58Z

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@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.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