Uninitialized memory used to generate nqn in nvmf_host_default()

[Alexander Potapenko]

Hi Christoph, Keith,

according to KMSAN (and common sense as well) the following code in
drivers/nvme/host/fabrics.c
(http://elixir.free-electrons.com/linux/latest/source/drivers/nvme/host/fabrics.c#L68):

  72         host = kmalloc(sizeof(*host), GFP_KERNEL);
  73         if (!host)
  74                 return NULL;
  75
  76         kref_init(&host->ref);
  77         snprintf(host->nqn, NVMF_NQN_SIZE,
  78                 "nqn.2014-08.org.nvmexpress:uuid:%pUb", &host->id);

uses uninitialized heap memory to generate the unique id for the NVMF host.
If I'm understanding correctly, it can be then passed to the
userspace, so the contents of the uninitialized chunk may potentially
leak.
If the specification doesn't rely on this UID to be random or unique,
I suggest using kzalloc() here, otherwise it might be a good idea to
use a real RNG.

Is my reasoning correct?

-- 
Alexander Potapenko
Software Engineer

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