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

[Luis Henriques <luis.henriques@canonical.com>]

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>
---
 drivers/block/zram/zcomp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 965d1afb0eaa..f3db8158e172 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -212,6 +212,7 @@ static int zcomp_strm_multi_create(struct zcomp *comp, int max_strm)
 	zstrm = zcomp_strm_alloc(comp);
 	if (!zstrm) {
 		kfree(zs);
+		comp->stream = NULL;
 		return -ENOMEM;
 	}
 	list_add(&zstrm->list, &zs->idle_strm);
@@ -262,6 +263,7 @@ static int zcomp_strm_single_create(struct zcomp *comp)
 	zs->zstrm = zcomp_strm_alloc(comp);
 	if (!zs->zstrm) {
 		kfree(zs);
+		comp->stream = NULL;
 		return -ENOMEM;
 	}
 	return 0;