linux-kernel - Re: [PATCH v2 4/5] drivers/misc/sgi-gru: fix dereference of ERR

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Date:	Thu, 3 Sep 2015 13:45:54 -0500
From:	Dimitri Sivanich <sivanich@....com>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/5] drivers/misc/sgi-gru: fix dereference of ERR_PTR

On Thu, Sep 03, 2015 at 08:20:50PM +0530, Sudip Mukherjee wrote:
> gru_alloc_gts() can fail and it can return ERR_PTR(errvalue). We should
> not dereference it if it has returned error. And incase it has returned
> error then wait for some time and try again.
> 
> Signed-off-by: Sudip Mukherjee <sudip@...torindia.org>
> ---
> 
> v2: on error retry after msleep(1).
> v1: returned error.
> 
>  drivers/misc/sgi-gru/grukservices.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/sgi-gru/grukservices.c b/drivers/misc/sgi-gru/grukservices.c
> index 490b79a..d64f2a0 100644
> --- a/drivers/misc/sgi-gru/grukservices.c
> +++ b/drivers/misc/sgi-gru/grukservices.c
> @@ -160,7 +160,14 @@ static void gru_load_kernel_context(struct gru_blade_state *bs, int blade_id)
>  	down_write(&bs->bs_kgts_sema);
>  
>  	if (!bs->bs_kgts) {
> -		bs->bs_kgts = gru_alloc_gts(NULL, 0, 0, 0, 0, 0);
> +		do {
> +			bs->bs_kgts = gru_alloc_gts(NULL, 0, 0, 0, 0, 0);
> +			if (IS_ERR(bs->bs_kgts)) {
> +				msleep(1);
> +				continue;
> +			}
> +			break;
> +		} while (true);

How about this way (for a little more compactness)?

+		do {
+			bs->bs_kgts = gru_alloc_gts(NULL, 0, 0, 0, 0, 0);
+			if (!IS_ERR(bs->bs_kgts))
+				break;
+			msleep(1)
+		} while (true);
>  		bs->bs_kgts->ts_user_blade_id = blade_id;
>  	}
>  	kgts = bs->bs_kgts;
> -- 
> 1.9.1
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