From: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Subject: zram: restrict add/remove attributes to root only
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.
[akpm@xxxxxxxxxxxxxxxxxxxx: s/sence/sense/, reflow comment to use 80 cols]
Fixes: 6566d1a32bf72 ("zram: add dynamic device add/remove functionality")
Link: http://lkml.kernel.org/r/20161205155845.20129-1-sergey.senozhatsky@xxxxxxxxx
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Reported-by: Steven Allen <steven@xxxxxxxxxxxxx>
Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.2+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff -puN drivers/block/zram/zram_drv.c~zram-restrict-add-remove-attributes-to-root-only drivers/block/zram/zram_drv.c
--- a/drivers/block/zram/zram_drv.c~zram-restrict-add-remove-attributes-to-root-only
+++ a/drivers/block/zram/zram_drv.c
@@ -1413,8 +1413,14 @@ static ssize_t hot_remove_store(struct c
return ret ? ret : count;
}
+/*
+ * NOTE: hot_add attribute is not the usual read-only sysfs attribute. In a
+ * sense 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,
};
_
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