Re: [PATCH] rdmavt: avoid NULL pointer dereference in rvt_qp_exit()

[Leon Romanovsky]

On Mon, Oct 17, 2022 at 05:26:52PM +0300, Natalia Petrova wrote:
> rvt_qp_exit() checks 'rdi->qp_dev' for NULL, but the pointer is
> dereferenced before that in rvt_free_all_qps().
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: f92e48718889 ("IB/rdmavt: Reset all QPs when the device is shut
> down")

Please never break fixes line.

> Signed-off-by: Natalia Petrova <n.petrova@xxxxxxxxxx>
> Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
> ---
>  drivers/infiniband/sw/rdmavt/qp.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c
> index 3acab569fbb9..06e755975f61 100644
> --- a/drivers/infiniband/sw/rdmavt/qp.c
> +++ b/drivers/infiniband/sw/rdmavt/qp.c
> @@ -459,13 +459,16 @@ static unsigned rvt_free_all_qps(struct rvt_dev_info *rdi)
>   */
>  void rvt_qp_exit(struct rvt_dev_info *rdi)
>  {
> -	u32 qps_inuse = rvt_free_all_qps(rdi);
> +	u32 qps_inuse = 0;
> +
> +	if (!rdi->qp_dev)
> +		return;
> +
> +	qps_inuse = rvt_free_all_qps(rdi);

These lines are not needed.

>  
>  	if (qps_inuse)
>  		rvt_pr_err(rdi, "QP memory leak! %u still in use\n",
>  			   qps_inuse);
> -	if (!rdi->qp_dev)
> -		return;

It is enough to delete these two lines. At this stage, rdi->qp_dev always
exists as it was created in rvt_register_device().

Thanks