linux-kernel - [RESEND PATCH v2] memory-hotplug: fix store_mem

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Date:   Wed, 31 Aug 2016 10:44:01 -0500
From:   Reza Arbab <arbab@...ux.vnet.ibm.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Yaowei Bai <baiyaowei@...s.chinamobile.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        Xishi Qiu <qiuxishi@...wei.com>,
        David Vrabel <david.vrabel@...rix.com>,
        Chen Yucong <slaoub@...il.com>,
        Andrew Banman <abanman@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return value

Attempting to online memory which is already online will cause this:

1. store_mem_state() called with buf="online"
2. device_online() returns 1 because device is already online
3. store_mem_state() returns 1
4. calling code interprets this as 1-byte buffer read
5. store_mem_state() called again with buf="nline"
6. store_mem_state() returns -EINVAL

Example:

$ cat /sys/devices/system/memory/memory0/state
online
$ echo online > /sys/devices/system/memory/memory0/state
-bash: echo: write error: Invalid argument

Fix the return value of store_mem_state() so this doesn't happen.

Signed-off-by: Reza Arbab <arbab@...ux.vnet.ibm.com>
---
Andrew et al, Greg asked that this come in through the -mm tree, as
you know this code better than him.

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

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 1cea0ba..8e385ea 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -359,7 +359,7 @@ store_mem_state(struct device *dev,
 err:
 	unlock_device_hotplug();
 
-	if (ret)
+	if (ret < 0)
 		return ret;
 	return count;
 }
-- 
1.8.3.1