linux-kernel - [PATCH v2] zram: fix possible use after free in zcomp

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Date:	Mon,  7 Sep 2015 15:13:10 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	Minchan Kim <minchan@...nel.org>, Nitin Gupta <ngupta@...are.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] zram: fix possible use after free in zcomp_create()

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@...r.kernel.org
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
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);
 	}
--
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