netdev - Re: [PATCH] netlink: fix state reallocation in policy export

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Message-ID: <20200819121006.7f6615e4@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 19 Aug 2020 12:10:06 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     netdev@...r.kernel.org, Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH] netlink: fix state reallocation in policy export

On Wed, 19 Aug 2020 12:22:55 +0200 Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@...el.com>
> 
> Evidently, when I did this previously, we didn't have more than
> 10 policies and didn't run into the reallocation path, because
> it's missing a memset() for the unused policies. Fix that.
> 
> Fixes: d07dcf9aadd6 ("netlink: add infrastructure to expose policies to userspace")
> Signed-off-by: Johannes Berg <johannes.berg@...el.com>
> ---
>  net/netlink/policy.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/netlink/policy.c b/net/netlink/policy.c
> index f6491853c797..3f3b421fd70c 100644
> --- a/net/netlink/policy.c
> +++ b/net/netlink/policy.c
> @@ -51,6 +51,9 @@ static int add_policy(struct nl_policy_dump **statep,
>  	if (!state)
>  		return -ENOMEM;
>  
> +	memset(&state->policies[state->n_alloc], 0,
> +	       sizeof(state->policies[0]) * (n_alloc - state->n_alloc));


[flex_]array_size() ? To avoid the inevitable follow up from a bot..