linux-kernel - [60/93] devmem: fix kmem write bug on memory holes

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Date:	Fri, 19 Feb 2010 08:29:53 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>,
	Nick Piggin <npiggin@...e.de>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Chuck Ebbert <cebbert@...hat.com>
Subject: [60/93] devmem: fix kmem write bug on memory holes

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------


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


commit c85e9a97c4102ce2e83112da850d838cfab5ab13 upstream

devmem: fix kmem write bug on memory holes

[ cebbert@...hat.com : backport to 2.6.32 ]

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.

Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
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: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Chuck Ebbert <cebbert@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/char/mem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -593,7 +593,7 @@ 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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