Patch "zram: fix possible use after free in zcomp_create()" has been added to the 4.2-stable tree

This is a note to let you know that I've just added the patch titled

zram: fix possible use after free in zcomp_create()

to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
zram-fix-possible-use-after-free-in-zcomp_create.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Luis Henriques <[email protected]>
Date: Thu, 17 Sep 2015 16:01:40 -0700
Subject: zram: fix possible use after free in zcomp_create()

From: Luis Henriques <[email protected]>

commit 3aaf14da807a4e9931a37f21e4251abb8a67021b upstream.

zcomp_create() verifies the success of zcomp_strm_{multi,single}_create() through comp->stream, which can potentially be pointing to memory that was freed if these functions returned an error.

While at it, replace a 'ERR_PTR(-ENOMEM)' by a more generic 'ERR_PTR(error)' as in the future zcomp_strm_{multi,siggle}_create() could return other error codes. Function documentation updated accordingly.

---
 drivers/block/zram/zcomp.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

@@ -330,12 +330,14 @@ void zcomp_destroy(struct zcomp *comp)
  * allocate new zcomp and initialize it. return compressing
  * backend pointer or ERR_PTR if things went bad. ERR_PTR(-EINVAL)
  * if requested algorithm is not supported, ERR_PTR(-ENOMEM) in
- * case of allocation error.
+ * case of allocation error, or any other error potentially
+ * returned by functions zcomp_strm_{multi,single}_create.
  */
 struct zcomp *zcomp_create(const char *compress, int max_strm)
 {
 	struct zcomp *comp;
 	struct zcomp_backend *backend;
+	int error;
 
 	backend = find_backend(compress);
 	if (!backend)

@@ -347,12 +349,12 @@ struct zcomp *zcomp_create(const char *c
 
 	comp->backend = backend;
 	if (max_strm > 1)
-		zcomp_strm_multi_create(comp, max_strm);
+		error = zcomp_strm_multi_create(comp, max_strm);
 	else
-		zcomp_strm_single_create(comp);
-	if (!comp->stream) {
+		error = zcomp_strm_single_create(comp);
+	if (error) {
 		kfree(comp);
-		return ERR_PTR(-ENOMEM);
+		return ERR_PTR(error);
 	}
 	return comp;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/zram-fix-possible-use-after-free-in-zcomp_create.patch