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

[Bart Van Assche]

On 3/4/23 21:07, Damien Le Moal wrote:
> A host ->queue_response() operation implementation may free the request
> passed as argument. Such implementation potentially could result
> in use after free of the request pointer when percpu_ref_put() is called
> in nvmet_req_complete().
> 
> Avoid such problem by using a local variable to save the sq pointer
> before calling __nvmet_req_complete(), thus avoiding dereferencing the
> req pointer.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal at opensource.wdc.com>

How about adding a Fixes: tag?

> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index 597d1b2c0d52..0f9193323a02 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -758,8 +758,10 @@ 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);

Interesting. The above patch looks similar to "[PATCH] nvmet: Fix a 
use-after-free" 
(https://lore.kernel.org/linux-nvme/20220812210317.2252051-1-bvanassche@acm.org/). 
One could wonder whether there are more occurrences of this pattern?

Bart.