[PATCH] nvme: initialize hostid uuid in nvmf_host_default to not leak kernel memory

[PATCH] nvme: initialize hostid uuid in nvmf_host_default to not leak kernel memory

[Johannes Thumshirn]

Alexander reports:
  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.

this assumption is correct so initialize the host->id using uuid_gen() as
it was done before commit 6bfe04255d5e ("nvme: add hostid token to fabric
options").

Fixes: 6bfe04255d5e ("nvme: add hostid token to fabric options")
Reported-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/nvme/host/fabrics.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 76b4fe6816a0..894c2ccb3891 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -74,6 +74,7 @@ static struct nvmf_host *nvmf_host_default(void)
 		return NULL;
 
 	kref_init(&host->ref);
+	uuid_gen(&host->id);
 	snprintf(host->nqn, NVMF_NQN_SIZE,
 		"nqn.2014-08.org.nvmexpress:uuid:%pUb", &host->id);
 
-- 
2.13.6

Re: [PATCH] nvme: initialize hostid uuid in nvmf_host_default to not leak kernel memory

[Christoph Hellwig]

I've already got the equivalent fix from Ewan queued up in nvme-4.15.

Re: [PATCH] nvme: initialize hostid uuid in nvmf_host_default to not leak kernel memory

[Keith Busch]

On Tue, Jan 09, 2018 at 04:20:43PM +0100, Johannes Thumshirn wrote:
> Alexander reports:
>   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.
> 
> this assumption is correct so initialize the host->id using uuid_gen() as
> it was done before commit 6bfe04255d5e ("nvme: add hostid token to fabric
> options").
> 
> Fixes: 6bfe04255d5e ("nvme: add hostid token to fabric options")
> Reported-by: Alexander Potapenko <glider@google.com>
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>

Thanks for the report and the fix. It'd still be good to use the kzalloc
variant in addition to this.

Reviewed-by: Keith Busch <keith.busch@intel.com>