linux-kernel - [PATCH 5.12 159/161] netfilter: nf_tables: missing error reporting for not selected expressions

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Date:   Tue,  8 Jun 2021 20:28:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pablo Neira Ayuso <pablo@...filter.org>
Subject: [PATCH 5.12 159/161] netfilter: nf_tables: missing error reporting for not selected expressions

From: Pablo Neira Ayuso <pablo@...filter.org>

commit c781471d67a56d7d4c113669a11ede0463b5c719 upstream.

Sometimes users forget to turn on nftables extensions from Kconfig that
they need. In such case, the error reporting from userspace is
misleading:

 $ sudo nft add rule x y counter
 Error: Could not process rule: No such file or directory
 add rule x y counter
 ^^^^^^^^^^^^^^^^^^^^

Add missing NL_SET_BAD_ATTR() to provide a hint:

 $ nft add rule x y counter
 Error: Could not process rule: No such file or directory
 add rule x y counter
              ^^^^^^^

Fixes: 83d9dcba06c5 ("netfilter: nf_tables: extended netlink error reporting for expressions")
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/netfilter/nf_tables_api.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3288,8 +3288,10 @@ static int nf_tables_newrule(struct net
 			if (n == NFT_RULE_MAXEXPRS)
 				goto err1;
 			err = nf_tables_expr_parse(&ctx, tmp, &info[n]);
-			if (err < 0)
+			if (err < 0) {
+				NL_SET_BAD_ATTR(extack, tmp);
 				goto err1;
+			}
 			size += info[n].ops->size;
 			n++;
 		}