linux-kernel - [stable] [PATCH] devmem: fix kmem write bug on memory holes

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Message-ID: <20100204024353.GA13576@localhost>
Date:	Thu, 4 Feb 2010 10:43:54 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Greg KH <greg@...ah.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"stable@...nel.org" <stable@...nel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: [stable] [PATCH] devmem: fix kmem write bug on memory holes

From: Wu Fengguang <fengguang.wu@...el.com>

commit c85e9a97c4102ce2e83112da850d838cfab5ab13 upstream.

write_kmem() used to assume vwrite() always return the full buffer length.
However now vwrite() could return 0 to indicate memory hole. This creates
a bug that "buf" is not advanced accordingly.

Fix it to simply ignore the return value, hence the memory hole.

CC: Andi Kleen <andi@...stfloor.org>
CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC: Christoph Lameter <cl@...ux-foundation.org>
CC: Ingo Molnar <mingo@...e.hu>
CC: Tejun Heo <tj@...nel.org>
CC: Nick Piggin <npiggin@...e.de>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC: <stable@...nel.org>
Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
---
 drivers/char/mem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-2.6.32.orig/drivers/char/mem.c	2010-02-04 10:37:55.000000000 +0800
+++ linux-2.6.32/drivers/char/mem.c	2010-02-04 10:37:59.000000000 +0800
@@ -599,7 +599,7 @@ static ssize_t write_kmem(struct file * 
 					break;
 				}
 			}
-			len = vwrite(kbuf, (char *)p, len);
+			vwrite(kbuf, (char *)p, len);
 			count -= len;
 			buf += len;
 			virtr += len;
--
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