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

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Date:	Thu,  5 May 2016 13:41:44 -0500
From:	Reza Arbab <arbab@...ux.vnet.ibm.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] 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>
---
 drivers/base/memory.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 961e2cf..031950f 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -359,9 +359,7 @@ store_mem_state(struct device *dev,
 err:
 	unlock_device_hotplug();

-	if (ret)
-		return ret;
-	return count;
+	return ret < 0 ? ret : count;
 }

 /*
-- 
1.8.3.1