[54/88] drivers/cdrom/cdrom.c: use kzalloc() for failing hardware

Steven Rostedt
2013-08-13T16:27:35Z

[-- Attachment #1: 0054-drivers-cdrom-cdrom.c-use-kzalloc-for-failing-hardwa.patch --]
[-- Type: text/plain, Size: 1770 bytes --]

3.6.11.7-rc1 stable review patch.
If anyone has any objections, please let me know.

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

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

[ Upstream commit 542db01579fbb7ea7d1f7bb9ddcef1559df660b2 ]

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
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;

--
1.7.10.4