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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	Minchan Kim <minchan@kernel.org>,
	Steven Allen <steven@stebalien.com>,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: [PATCHv3] zram: restrict add/remove attributes to root only
Date: Tue,  6 Dec 2016 00:58:45 +0900
Message-ID: <20161205155845.20129-1-sergey.senozhatsky@gmail.com> (raw)
In-Reply-To: <20161204124413.22595-1-sergey.senozhatsky@gmail.com>

zram hot_add sysfs attribute is a very 'special' attribute - reading
from it creates a new uninitialized zram device. This file, by a mistake,
can be read by a 'normal' user at the moment, while only root must be
able to create a new zram device, therefore hot_add attribute must have
S_IRUSR mode, not S_IRUGO.

Fixes: 6566d1a32bf72 ("zram: add dynamic device add/remove functionality")
Reported-by: Steven Allen <steven@stebalien.com>
Cc: <stable@vger.kernel.org>    [4.2+]
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 drivers/block/zram/zram_drv.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 5163c8f..cc8d0b5 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1413,8 +1413,15 @@ static ssize_t hot_remove_store(struct class *class,
 	return ret ? ret : count;
 }
 
+/*
+ * NOTE: hot_add attribute is not the usual read-only sysfs
+ * attribute. In a sence that reading from this file does alter
+ * the state of your system -- it creates a new un-initialized
+ * zram device and returns back this device's device_id (or an
+ * error code if it fails to create a new device).
+ */
 static struct class_attribute zram_control_class_attrs[] = {
-	__ATTR_RO(hot_add),
+	__ATTR(hot_add, 0400, hot_add_show, NULL),
 	__ATTR_WO(hot_remove),
 	__ATTR_NULL,
 };
-- 
2.10.2

  parent reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-04 12:44 [PATCHv2] " Sergey Senozhatsky
2016-12-05 12:57 ` Greg KH
2016-12-05 15:57   ` Sergey Senozhatsky
2016-12-05 15:58 ` Sergey Senozhatsky [this message]
2016-12-05 16:50   ` [PATCHv3] " Greg KH

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