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>

diff --git a/fs/char_dev.c b/fs/char_dev.c
index a279c58..8a63cfa 100644 (file)
--- 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;