linux-kernel - [PATCH] zram: restrict add/remove attributes to root only

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Message-Id: <20161204023515.7740-1-sergey.senozhatsky@gmail.com>
Date:   Sun,  4 Dec 2016 11:35:15 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Minchan Kim <minchan@...nel.org>,
        Steven Allen <steven@...balien.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [PATCH] zram: restrict add/remove attributes to root only

Only root must be able to create a new zram device, therefore
hot_add attribute must have S_IRUSR mode, not S_IRUGO. Otherwise,
anyone can create a new zram device (device initialization with
the disksize attr requires root permission).

Fixes: 6566d1a32bf72 ("zram: add dynamic device add/remove functionality")
Reported-by: Steven Allen <steven@...balien.com>
Cc: <stable@...r.kernel.org>    [4.2+]
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
---
 drivers/block/zram/zram_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 5163c8f..ee03464 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1414,8 +1414,8 @@ static ssize_t hot_remove_store(struct class *class,
 }
 
 static struct class_attribute zram_control_class_attrs[] = {
-	__ATTR_RO(hot_add),
-	__ATTR_WO(hot_remove),
+	__ATTR(hot_add, 0400, hot_add_show, NULL),
+	__ATTR(hot_remove, 0200, NULL, hot_remove_store),
 	__ATTR_NULL,
 };
 
-- 
2.10.2