From 65ec64f28a882096d9976963e2ccefd85085fb1a Mon Sep 17 00:00:00 2001
From: Chengguang Xu <cgxu519@gmx.com>
Date: Fri, 15 Feb 2019 20:27:11 +0800
Subject: [PATCH] chardev: add additional check for minor range overlap

[ Upstream commit de36e16d1557a0b6eb328bc3516359a12ba5c25c ]

Current overlap checking cannot correctly handle
a case which is baseminor < existing baseminor &&
baseminor + minorct > existing baseminor + minorct.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/char_dev.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/char_dev.c b/fs/char_dev.c
index a279c58..8a63cfa 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -159,6 +159,12 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
 			ret = -EBUSY;
 			goto out;
 		}
+
+		if (new_min < old_min && new_max > old_max) {
+			ret = -EBUSY;
+			goto out;
+		}
+
 	}
 
 	cd->next = *cp;
-- 
2.7.4