[PATCH 16/29] drivers, media: convert vb2_vmalloc_buf.refcount from atomic_t to refcount_t

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

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-vmalloc.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c
index 3f77814..f83253a 100644
--- a/drivers/media/v4l2-core/videobuf2-vmalloc.c
+++ b/drivers/media/v4l2-core/videobuf2-vmalloc.c
@@ -13,6 +13,7 @@
#include <linux/io.h>
#include <linux/module.h>
#include <linux/mm.h>
+#include <linux/refcount.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
@@ -26,7 +27,7 @@ struct vb2_vmalloc_buf {
struct frame_vector *vec;
enum dma_data_direction dma_dir;
unsigned long size;
- atomic_t refcount;
+ refcount_t refcount;
struct vb2_vmarea_handler handler;
struct dma_buf *dbuf;
};
@@ -56,7 +57,7 @@ static void *vb2_vmalloc_alloc(struct device *dev, unsigned long attrs,
return ERR_PTR(-ENOMEM);
}

- atomic_inc(&buf->refcount);
+ refcount_set(&buf->refcount, 1);
return buf;
}

@@ -64,7 +65,7 @@ static void vb2_vmalloc_put(void *buf_priv)
{
struct vb2_vmalloc_buf *buf = buf_priv;

- if (atomic_dec_and_test(&buf->refcount)) {
+ if (refcount_dec_and_test(&buf->refcount)) {
vfree(buf->vaddr);
kfree(buf);
}
@@ -161,7 +162,7 @@ static void *vb2_vmalloc_vaddr(void *buf_priv)
static unsigned int vb2_vmalloc_num_users(void *buf_priv)
{
struct vb2_vmalloc_buf *buf = buf_priv;
- return atomic_read(&buf->refcount);
+ return refcount_read(&buf->refcount);
}

static int vb2_vmalloc_mmap(void *buf_priv, struct vm_area_struct *vma)
@@ -368,7 +369,7 @@ static struct dma_buf *vb2_vmalloc_get_dmabuf(void *buf_priv, unsigned long flag
return NULL;

/* dmabuf keeps reference to vb2 buffer */
- atomic_inc(&buf->refcount);
+ refcount_inc(&buf->refcount);

return dbuf;
}
--
2.7.4

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