Subject: Re: [PATCH net] net/sched: cls_flower: allocate mask dynamically in fl_change()

From: Jiri Pirko <[email-masked]>
Date: Wed, 16 Jan 2019 16:24:36 +0100

Wed, Jan 16, 2019 at 04:02:10PM CET, [email-masked] wrote:
>Recent changes (especially 05cd271fd61a ("cls_flower: Support multiple
>masks per priority")) in the fl_flow_mask structure grow it and its
>current size e.g. on x86_64 with defconfig is 760 bytes and more than
>1024 bytes with some debug options enabled. Prior the mentioned commit
>its size was 176 bytes (using defconfig on x86_64).
>With regard to this fact it's reasonable to allocate this structure
>dynamically in fl_change() to reduce its stack size.
>
>Fixes: 05cd271fd61a ("cls_flower: Support multiple masks per priority")

Not sure this is -net material. But I don't mind.

>Cc: Jiri Pirko <[email-masked]>
>Cc: Paul Blakey <[email-masked]>
>Signed-off-by: Ivan Vecera <[email-masked]>
>---
> net/sched/cls_flower.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
>diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
>index dad04e710493..47ac88cc34fb 100644
>--- a/net/sched/cls_flower.c
>+++ b/net/sched/cls_flower.c
>@@ -1291,16 +1291,22 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
> 	struct cls_fl_filter *fold = *arg;
> 	struct cls_fl_filter *fnew;
> 	struct nlattr **tb;
>-	struct fl_flow_mask mask = {};
>+	struct fl_flow_mask *mask;
> 	int err;
> 
> 	if (!tca[TCA_OPTIONS])
> 		return -EINVAL;
> 
>-	tb = kcalloc(TCA_FLOWER_MAX + 1, sizeof(struct nlattr *), GFP_KERNEL);
>-	if (!tb)
>+	mask = kcalloc(1, sizeof(struct fl_flow_mask), GFP_KERNEL);

kzalloc?

Otherwise this looks fine.
Acked-by: Jiri Pirko <[email-masked]>

>+	if (!mask)
> 		return -ENOBUFS;
> 
>+	tb = kcalloc(TCA_FLOWER_MAX + 1, sizeof(struct nlattr *), GFP_KERNEL);
>+	if (!tb) {
>+		err = -ENOBUFS;
>+		goto errout_mask_alloc;
>+	}
>+
> 	err = nla_parse_nested(tb, TCA_FLOWER_MAX, tca[TCA_OPTIONS],
> 			       fl_policy, NULL);
> 	if (err < 0)
>@@ -1343,12 +1349,12 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
> 		}
> 	}
> 
>-	err = fl_set_parms(net, tp, fnew, &mask, base, tb, tca[TCA_RATE], ovr,
>+	err = fl_set_parms(net, tp, fnew, mask, base, tb, tca[TCA_RATE], ovr,
> 			   tp->chain->tmplt_priv, extack);
> 	if (err)
> 		goto errout_idr;
> 
>-	err = fl_check_assign_mask(head, fnew, fold, &mask);
>+	err = fl_check_assign_mask(head, fnew, fold, mask);
> 	if (err)
> 		goto errout_idr;
> 
>@@ -1392,6 +1398,7 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
> 	}
> 
> 	kfree(tb);
>+	kfree(mask);
> 	return 0;
> 
> errout_mask:
>@@ -1405,6 +1412,8 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
> 	kfree(fnew);
> errout_tb:
> 	kfree(tb);
>+errout_mask_alloc:
>+	kfree(mask);
> 	return err;
> }
> 
>-- 
>2.19.2
>