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SubjectRe: [PATCH] zram: fix possible use after free in zcomp_create()
On Mon, Sep 07, 2015 at 08:11:48PM +0900, Sergey Senozhatsky wrote:
> On (09/07/15 11:33), 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.
> >
>
> good catch.
>
> we probably better start checking the zcomp_strm_multi_create()/
> zcomp_strm_single_create() status in zcomp_create(); that's much
> more obvious and that's why we return it in the first place.
>
> what do you think?
>

Yep, that's probably a better solution.

Acked-by: Luis Henriques <luis.henriques@canonical.com>

Cheers,
--
Luís

> ---
>
> 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 3456d5a..16bbc8c 100644
> --- a/drivers/block/zram/zcomp.c
> +++ b/drivers/block/zram/zcomp.c
> @@ -360,6 +360,7 @@ 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)
> @@ -371,10 +372,10 @@ 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 != 0) {
> kfree(comp);
> return ERR_PTR(-ENOMEM);
> }
>


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