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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Chengguang Xu <cgxu519@gmx.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 104/128] chardev: add additional check for minor range overlap
Date:   Wed, 29 May 2019 20:07:16 -0700
Message-Id: <20190530030453.326003210@linuxfoundation.org>
In-Reply-To: <20190530030432.977908967@linuxfoundation.org>
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[ 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>
---
 fs/char_dev.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 44a240c4bb658..a112a4745d8b3 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -134,6 +134,12 @@ __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