linux-kernel - Re: [PATCH 4.19 233/422] netfilter: nf_tables: avoid BUG

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Date:   Thu, 21 Nov 2019 21:16:18 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 233/422] netfilter: nf_tables: avoid BUG_ON usage

Hi!

> From: Florian Westphal <fw@...len.de>
> 
> [ Upstream commit fa5950e498e7face21a1761f327e6c1152f778c3 ]
> 
> None of these spots really needs to crash the kernel.
> In one two cases we can jsut report error to userspace, in the other
> cases we can just use WARN_ON (and leak memory instead).

Do these conditions trigger for someone, to warrant -stable patch?

> +++ b/net/netfilter/nft_cmp.c
> @@ -79,7 +79,8 @@ static int nft_cmp_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
>  
>  	err = nft_data_init(NULL, &priv->data, sizeof(priv->data), &desc,
>  			    tb[NFTA_CMP_DATA]);
> -	BUG_ON(err < 0);
> +	if (err < 0)
> +		return err;
>  
>  	priv->sreg = nft_parse_register(tb[NFTA_CMP_SREG]);
>  	err = nft_validate_register_load(priv->sreg, desc.len);
> @@ -129,7 +130,8 @@ static int nft_cmp_fast_init(const struct nft_ctx *ctx,
>  
>  	err = nft_data_init(NULL, &data, sizeof(data), &desc,
>  			    tb[NFTA_CMP_DATA]);
> -	BUG_ON(err < 0);
> +	if (err < 0)
> +		return err;
>  
>  	priv->sreg = nft_parse_register(tb[NFTA_CMP_SREG]);
>  	err = nft_validate_register_load(priv->sreg, desc.len);

This goes from "kill kernel with backtrace" to "silently return
failure". Should WARN_ON() be preserved here?

Best regards,
								Pavel
								
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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