[PATCH v3 1/4] chardev: add additional check for minor range overlap

[Chengguang Xu]

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>
---
v1->v2:
- Split fix and cleanup patches.
- Remove printing minor range in chrdev_show().

 fs/char_dev.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/char_dev.c b/fs/char_dev.c
index a279c58fe360..8a63cfa29005 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