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    Subject[PATCH 86/98] drivers/cdrom/cdrom.c: use kzalloc() for failing hardware
    Date
    3.5.7.17 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Jonathan Salwan <jonathan.salwan@gmail.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@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: Luis Henriques <luis.henriques@canonical.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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