[PATCH 5.0 244/346] chardev: add additional check for minor range overlap

[Greg Kroah-Hartman]

[ 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 <cgxu...@gmx.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Sasha Levin <sas...@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 a279c58fe3606..8a63cfa290053 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;
-- 
2.20.1