netdev - [PATCH][next] netfilter: nftables: fix incorrect increment of loop counter

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Date:   Mon, 14 Dec 2020 23:40:15 +0000
From:   Colin King <colin.king@...onical.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] netfilter: nftables: fix incorrect increment of loop counter

From: Colin Ian King <colin.king@...onical.com>

The intention of the err_expr cleanup path is to iterate over the
allocated expr_array objects and free them, starting from i - 1 and
working down to the start of the array. Currently the loop counter
is being incremented instead of decremented and also the index i is
being used instead of k, repeatedly destroying the same expr_array
element.  Fix this by decrementing k and using k as the index into
expr_array.

Addresses-Coverity: ("Infinite loop")
Fixes: 8cfd9b0f8515 ("netfilter: nftables: generalize set expressions support")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 net/netfilter/nf_tables_api.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 8d5aa0ac45f4..4186b1e52d58 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -5254,8 +5254,8 @@ static int nft_set_elem_expr_clone(const struct nft_ctx *ctx,
 	return 0;
 
 err_expr:
-	for (k = i - 1; k >= 0; k++)
-		nft_expr_destroy(ctx, expr_array[i]);
+	for (k = i - 1; k >= 0; k--)
+		nft_expr_destroy(ctx, expr_array[k]);
 
 	return -ENOMEM;
 }
-- 
2.29.2