[PATCH 4.19 210/276] chardev: add additional check for minor range overlap

From: Greg Kroah-Hartman
Date: Thu May 30 2019 - 00:08:03 EST


[ 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@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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