Re: [PATCH v2] zram: fix possible use after free in zcomp_create()

[Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>]

On (09/07/15 15:13), Luis Henriques wrote:
> zcomp_create() verifies the success of zcomp_strm_{multi,siggle}_create()
> through comp->stream, which can potentially be pointing to memory that was
> freed if these functions returned an error.
> 
> Fixes: beca3ec71fe5 ("zram: add multi stream functionality")
> Cc: stable@vger.kernel.org
> Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

Cc Andrew


Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

	-ss

> ---
> Changes since v1:
>  * Check zcomp_strm_{multi,siggle}_create() return code instead
>    comp->stream (suggested by Sergey)
> 
> drivers/block/zram/zcomp.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> index 965d1afb0eaa..8d2cdfd307db 100644
> --- a/drivers/block/zram/zcomp.c
> +++ b/drivers/block/zram/zcomp.c
> @@ -336,6 +336,7 @@ struct zcomp *zcomp_create(const char *compress, int max_strm)
>  {
>  	struct zcomp *comp;
>  	struct zcomp_backend *backend;
> +	int ret;
>  
>  	backend = find_backend(compress);
>  	if (!backend)
> @@ -347,10 +348,10 @@ struct zcomp *zcomp_create(const char *compress, int max_strm)
>  
>  	comp->backend = backend;
>  	if (max_strm > 1)
> -		zcomp_strm_multi_create(comp, max_strm);
> +		ret = zcomp_strm_multi_create(comp, max_strm);
>  	else
> -		zcomp_strm_single_create(comp);
> -	if (!comp->stream) {
> +		ret = zcomp_strm_single_create(comp);
> +	if (ret) {
>  		kfree(comp);
>  		return ERR_PTR(-ENOMEM);
>  	}
>