linux-kernel - [PATCH 091/145] drivers/cdrom/cdrom.c: use kzalloc() for failing hardware

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Message-Id: <1374101277-7915-92-git-send-email-kamal@canonical.com>
Date:	Wed, 17 Jul 2013 15:47:03 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 091/145] drivers/cdrom/cdrom.c: use kzalloc() for failing hardware

3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jonathan Salwan <jonathan.salwan@...il.com>

commit 542db01579fbb7ea7d1f7bb9ddcef1559df660b2 upstream.

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@...cle.com>
Cc: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/cdrom/cdrom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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;
 
-- 
1.8.1.2

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