From 050e4b8fb7cdd7096c987a9cd556029c622c7fe2 Mon Sep 17 00:00:00 2001
From: Jonathan Salwan <jonathan.salwan@gmail.com>
Date: Thu, 06 Jun 2013 00:39:39 +0000
Subject: drivers/cdrom/cdrom.c: use kzalloc() for failing hardware

In drivers/cdrom/cdrom.c mmc_ioctl_cdrom_read_data() allocates a memory
area with kmalloc in line 2885.

2885         cgc->buffer = kmalloc(blocksize, GFP_KERNEL);
2886         if (cgc->buffer == NULL)
2887                 return -ENOMEM;

In line 2908 we can find the copy_to_user function:

2908         if (!ret && copy_to_user(arg, cgc->buffer, blocksize))

The cgc->buffer is never cleaned and initialized before this function.  If
ret = 0 with the previous basic block, it's possible to display some
memory bytes in kernel space from userspace.

When we read a block from the disk it normally fills the ->buffer but if
the drive is malfunctioning there is a chance that it would only be
partially filled.  The result is an leak information to userspace.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
(limited to 'drivers/cdrom/cdrom.c')

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index d620b44..8a3aff7 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -2882,7 +2882,7 @@ static noinline int mmc_ioctl_cdrom_read_data(struct cdrom_device_info *cdi,
 	if (lba < 0)
 		return -EINVAL;
 
-	cgc->buffer = kmalloc(blocksize, GFP_KERNEL);
+	cgc->buffer = kzalloc(blocksize, GFP_KERNEL);
 	if (cgc->buffer == NULL)
 		return -ENOMEM;
 
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