[PATCH v2] nvmet: Avoid potential UAF in nvmet_req_complete()

[Sagi Grimberg]

Hey Damien,

> An nvme target ->queue_response() operation implementation may free the
> request passed as argument. Such implementation potentially could result
> in a use after free of the request pointer when percpu_ref_put() is
> called in nvmet_req_complete().

Can you point me to which transport frees the request?

> 
> Avoid such problem by using a local variable to save the sq pointer
> before calling __nvmet_req_complete(), thus avoiding dereferencing the
> req pointer after that function call.
> 
> Fixes: a07b4970f464 ("nvmet: add a generic NVMe target")
> Cc: stable at vger.kernel.org
> Signed-off-by: Damien Le Moal <damien.lemoal at opensource.wdc.com>
> ---
> 
> Changes from v1:
>   * Added Fixes tag and cc stable
> 
>   drivers/nvme/target/core.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index f66ed13d7c11..3935165048e7 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -756,8 +756,10 @@ static void __nvmet_req_complete(struct nvmet_req *req, u16 status)
>   
>   void nvmet_req_complete(struct nvmet_req *req, u16 status)
>   {
> +	struct nvmet_sq *sq = req->sq;
> +
>   	__nvmet_req_complete(req, status);
> -	percpu_ref_put(&req->sq->ref);
> +	percpu_ref_put(&sq->ref);
>   }
>   EXPORT_SYMBOL_GPL(nvmet_req_complete);
>