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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, Christoph Hellwig <hch@lst.de>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 4.16 63/81] cdrom: information leak in cdrom_ioctl_media_changed()
Date:   Fri, 27 Apr 2018 15:59:05 +0200
Message-Id: <20180427135747.011303979@linuxfoundation.org>
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4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@oracle.com>

commit 9de4ee40547fd315d4a0ed1dd15a2fa3559ad707 upstream.

This cast is wrong.  "cdi->capacity" is an int and "arg" is an unsigned
long.  The way the check is written now, if one of the high 32 bits is
set then we could read outside the info->slots[] array.

This bug is pretty old and it predates git.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/cdrom/cdrom.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -2374,7 +2374,7 @@ static int cdrom_ioctl_media_changed(str
 	if (!CDROM_CAN(CDC_SELECT_DISC) || arg == CDSL_CURRENT)
 		return media_changed(cdi, 1);
 
-	if ((unsigned int)arg >= cdi->capacity)
+	if (arg >= cdi->capacity)
 		return -EINVAL;
 
 	info = kmalloc(sizeof(*info), GFP_KERNEL);