RE: [PATCH v2] IB/hfi1: Prevent a NULL dereference

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> -----Original Message-----
> From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Dan Carpenter
> Sent: Tuesday, January 9, 2018 3:04 PM
> To: Marciniszyn, Mike <mike.marciniszyn@xxxxxxxxx>
> Cc: Dalessandro, Dennis <dennis.dalessandro@xxxxxxxxx>; Doug Ledford
> <dledford@xxxxxxxxxx>; Jason Gunthorpe <jgg@xxxxxxxx>; linux-
> rdma@xxxxxxxxxxxxxxx; kernel-janitors@xxxxxxxxxxxxxxx
> Subject: [PATCH v2] IB/hfi1: Prevent a NULL dereference
> 
> In the original code, we set "fd->uctxt" to NULL and then dereference it
> which will cause an Oops.
> 
> Fixes: f2a3bc00a03c ("IB/hfi1: Protect context array set/clear with spinlock")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> v2: In v1, I accidentally moved the __clear_bit() out from under the
>     spin_lock().  Thanks for the review, Michael!
> 
> diff --git a/drivers/infiniband/hw/hfi1/file_ops.c
> b/drivers/infiniband/hw/hfi1/file_ops.c
> index 82086241aac3..bd6f03cc5ee0 100644
> --- a/drivers/infiniband/hw/hfi1/file_ops.c
> +++ b/drivers/infiniband/hw/hfi1/file_ops.c
> @@ -763,11 +763,11 @@ static int complete_subctxt(struct hfi1_filedata *fd)
>  	}
> 
>  	if (ret) {
> -		hfi1_rcd_put(fd->uctxt);
> -		fd->uctxt = NULL;
>  		spin_lock_irqsave(&fd->dd->uctxt_lock, flags);
>  		__clear_bit(fd->subctxt, fd->uctxt->in_use_ctxts);
>  		spin_unlock_irqrestore(&fd->dd->uctxt_lock, flags);
> +		hfi1_rcd_put(fd->uctxt);
> +		fd->uctxt = NULL;
>  	}
> 
>  	return ret;
> --

Cc: <stable@xxxxxxxxxxxxxxx> # 4.14.x
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@xxxxxxxxx>

Looks good.  Adding tag for stable too.

Thanks,

Mike

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