[CRIU] [PATCH] lazy_image(): avoid NULL deref

[Andrew Vagin]

On Thu, Apr 30, 2015 at 04:25:43PM -0700, Kir Kolyshkin wrote:
> Do check img before deferefencing, just as in empty_image().

I would prefer to remove this check from empty_image(). A caller of
open_image() must handler errors.

We can add this check into close_image() jast as in xfree().

diff --git a/image.c b/image.c
index 7f3ceb5..a6bc3f1 100644
--- a/image.c
+++ b/image.c
@@ -359,6 +359,8 @@ int open_image_lazy(struct cr_img *img)
 
 void close_image(struct cr_img *img)
 {
+       if (img == NULL)
+               return;
        if (lazy_image(img))
                xfree(img->path);
        else if (!empty_image(img))

> This is an addition to commit 8ce37e67.
> 
> Signed-off-by: Kir Kolyshkin <kir at openvz.org>
> ---
>  include/image.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/image.h b/include/image.h
> index 55e63dd..76ad2e8 100644
> --- a/include/image.h
> +++ b/include/image.h
> @@ -146,7 +146,7 @@ static inline bool empty_image(struct cr_img *img)
>  
>  static inline bool lazy_image(struct cr_img *img)
>  {
> -	return img->_x.fd == LAZY_IMG_FD;
> +	return img && img->_x.fd == LAZY_IMG_FD;
>  }
>  
>  extern int open_image_lazy(struct cr_img *img);
> -- 
> 1.9.3
>