linux-kernel - [PATCH] staging: zsmalloc: Ensure handle is never 0 on success

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Message-Id: <1383699252-8898-1-git-send-email-ohaugan@codeaurora.org>
Date:	Tue,  5 Nov 2013 16:54:12 -0800
From:	Olav Haugan <ohaugan@...eaurora.org>
To:	gregkh@...uxfoundation.org
Cc:	ngupta@...are.org, sjenning@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, minchan@...nel.org,
	linux-arm-msm@...r.kernel.org, Olav Haugan <ohaugan@...eaurora.org>
Subject: [PATCH] staging: zsmalloc: Ensure handle is never 0 on success

zsmalloc encodes a handle using the page pfn and an object
index. On some hardware platforms the pfn could be 0 and this
causes the encoded handle to be 0 which is interpreted as an
allocation failure.

To prevent this false error we ensure that the encoded handle
will not be 0 when allocation succeeds.

Change-Id: Ifff930dcf254915b497aec5cb36f152a5e5365d6
Signed-off-by: Olav Haugan <ohaugan@...eaurora.org>
---
 drivers/staging/zsmalloc/zsmalloc-main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
index 523b937..0e32c0f 100644
--- a/drivers/staging/zsmalloc/zsmalloc-main.c
+++ b/drivers/staging/zsmalloc/zsmalloc-main.c
@@ -441,7 +441,7 @@ static void *obj_location_to_handle(struct page *page, unsigned long obj_idx)
 	}
 
 	handle = page_to_pfn(page) << OBJ_INDEX_BITS;
-	handle |= (obj_idx & OBJ_INDEX_MASK);
+	handle |= ((obj_idx + 1) & OBJ_INDEX_MASK);
 
 	return (void *)handle;
 }
@@ -451,7 +451,7 @@ static void obj_handle_to_location(unsigned long handle, struct page **page,
 				unsigned long *obj_idx)
 {
 	*page = pfn_to_page(handle >> OBJ_INDEX_BITS);
-	*obj_idx = handle & OBJ_INDEX_MASK;
+	*obj_idx = (handle & OBJ_INDEX_MASK) - 1;
 }
 
 static unsigned long obj_idx_to_offset(struct page *page,
-- 
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