[PATCH 13/29] drivers, media: convert vb2_vmarea_handler.refcount from atomic_t to refcount_t

Elena Reshetova
2017-03-06T14:21:00Z

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/v4l2-core/videobuf2-memops.c | 6 +++---
include/media/videobuf2-memops.h | 3 ++-
2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-memops.c b/drivers/media/v4l2-core/videobuf2-memops.c
index 1cd322e..4bb8424 100644
--- a/drivers/media/v4l2-core/videobuf2-memops.c
+++ b/drivers/media/v4l2-core/videobuf2-memops.c
@@ -96,10 +96,10 @@ static void vb2_common_vm_open(struct vm_area_struct *vma)
struct vb2_vmarea_handler *h = vma->vm_private_data;

pr_debug("%s: %p, refcount: %d, vma: %08lx-%08lx\n",
- __func__, h, atomic_read(h->refcount), vma->vm_start,
+ __func__, h, refcount_read(h->refcount), vma->vm_start,
vma->vm_end);

- atomic_inc(h->refcount);
+ refcount_inc(h->refcount);
}

/**
@@ -114,7 +114,7 @@ static void vb2_common_vm_close(struct vm_area_struct *vma)
struct vb2_vmarea_handler *h = vma->vm_private_data;

pr_debug("%s: %p, refcount: %d, vma: %08lx-%08lx\n",
- __func__, h, atomic_read(h->refcount), vma->vm_start,
+ __func__, h, refcount_read(h->refcount), vma->vm_start,
vma->vm_end);

h->put(h->arg);
diff --git a/include/media/videobuf2-memops.h b/include/media/videobuf2-memops.h
index 36565c7a..a6ed091 100644
--- a/include/media/videobuf2-memops.h
+++ b/include/media/videobuf2-memops.h
@@ -16,6 +16,7 @@

#include <media/videobuf2-v4l2.h>
#include <linux/mm.h>
+#include <linux/refcount.h>

/**
* struct vb2_vmarea_handler - common vma refcount tracking handler
@@ -25,7 +26,7 @@
* @arg: argument for @put callback
*/
struct vb2_vmarea_handler {
- atomic_t *refcount;
+ refcount_t *refcount;
void (*put)(void *arg);
void *arg;
};
--
2.7.4