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

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Message-Id: <20190405112711.25275-1-cgxu519@gmx.com>
Date:   Fri,  5 Apr 2019 19:27:08 +0800
From:   Chengguang Xu <cgxu519@....com>
To:     gregkh@...uxfoundation.org, dan.carpenter@...cle.com
Cc:     linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
        linux-kernel@...r.kernel.org, Chengguang Xu <cgxu519@....com>
Subject: [PATCH v3 1/4] chardev: add additional check for minor range overlap

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

Signed-off-by: Chengguang Xu <cgxu519@....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