linux-kernel - [PATCH 2/2] staging: zcache: fix memory corruption bug

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Date:	Tue, 28 Feb 2012 16:02:23 -0600
From:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Nitin Gupta <ngupta@...are.org>,
	Robert Jennings <rcj@...ux.vnet.ibm.com>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] staging: zcache: fix memory corruption bug

This patch fixes a bug where the zv code writes before the allocated
buffer, resulting in system memory corruption. This was introduced
during the switch from xvmalloc to zsmalloc.

Signed-off-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
---
 drivers/staging/zcache/zcache-main.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 46c7c04..7073465 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -701,7 +701,6 @@ static struct zv_hdr *zv_create(struct zs_pool *pool, uint32_t pool_id,
 	u32 size = clen + sizeof(struct zv_hdr);
 	int chunks = (size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT;
 	void *handle = NULL;
-	char *buf;
 
 	BUG_ON(!irqs_disabled());
 	BUG_ON(chunks >= NCHUNKS);
@@ -710,14 +709,13 @@ static struct zv_hdr *zv_create(struct zs_pool *pool, uint32_t pool_id,
 		goto out;
 	atomic_inc(&zv_curr_dist_counts[chunks]);
 	atomic_inc(&zv_cumul_dist_counts[chunks]);
-	zv = (struct zv_hdr *)((char *)cdata - sizeof(*zv));
+	zv = zs_map_object(pool, handle);
 	zv->index = index;
 	zv->oid = *oid;
 	zv->pool_id = pool_id;
 	zv->size = clen;
 	SET_SENTINEL(zv, ZVH);
-	buf = zs_map_object(pool, handle);
-	memcpy(buf, zv, clen + sizeof(*zv));
+	memcpy((char *)zv + sizeof(struct zv_hdr), cdata, clen);
 	zs_unmap_object(pool, handle);
 out:
 	return handle;
-- 
1.7.5.4

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