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From: Walter Harms <wharms@bfs.de>
To: Colin King <colin.king@canonical.com>,
	Pablo Neira Ayuso <pablo@netfilter.org>,
	Jozsef Kadlecsik <kadlec@netfilter.org>,
	"Florian Westphal" <fw@strlen.de>,
	"David S . Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"netfilter-devel@vger.kernel.org"
	<netfilter-devel@vger.kernel.org>,
	"coreteam@netfilter.org" <coreteam@netfilter.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Cc: "kernel-janitors@vger.kernel.org"
	<kernel-janitors@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: AW: [PATCH][next] netfilter: nf_tables: Fix dereference of null pointer flow
Date: Fri, 25 Jun 2021 10:06:26 +0000	[thread overview]
Message-ID: <b9c2377849aa4ac38ab0306589eb22d2@bfs.de> (raw)
In-Reply-To: <20210624195718.170796-1-colin.king@canonical.com>

hi Colin,
most free_something_functions accept NULL
these days, perhaps it would be more efficient
to add a check in nft_flow_rule_destroy().
There is a chance that this will catch the same
mistake in future  also.

jm2c,
re,
 wh
________________________________________
Von: Colin King <colin.king@canonical.com>
Gesendet: Donnerstag, 24. Juni 2021 21:57:18
An: Pablo Neira Ayuso; Jozsef Kadlecsik; Florian Westphal; David S . Miller; Jakub Kicinski; netfilter-devel@vger.kernel.org; coreteam@netfilter.org; netdev@vger.kernel.org
Cc: kernel-janitors@vger.kernel.org; linux-kernel@vger.kernel.org
Betreff: [PATCH][next] netfilter: nf_tables: Fix dereference of null pointer flow

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

In the case where chain->flags & NFT_CHAIN_HW_OFFLOAD is false then
nft_flow_rule_create is not called and flow is NULL. The subsequent
error handling execution via label err_destroy_flow_rule will lead
to a null pointer dereference on flow when calling nft_flow_rule_destroy.
Since the error path to err_destroy_flow_rule has to cater for null
and non-null flows, only call nft_flow_rule_destroy if flow is non-null
to fix this issue.

Addresses-Coverity: ("Explicity null dereference")
Fixes: 3c5e44622011 ("netfilter: nf_tables: memleak in hw offload abort path")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 net/netfilter/nf_tables_api.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 390d4466567f..de182d1f7c4e 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3446,7 +3446,8 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
        return 0;

 err_destroy_flow_rule:
-       nft_flow_rule_destroy(flow);
+       if (flow)
+               nft_flow_rule_destroy(flow);
 err_release_rule:
        nf_tables_rule_release(&ctx, rule);
 err_release_expr:
--
2.31.1


  parent reply	other threads:[~2021-06-25 10:14 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24 19:57 Colin King
2021-06-25  9:59 ` Dan Carpenter
2021-06-25 10:20   ` Pablo Neira Ayuso
2021-06-25 10:33     ` Dan Carpenter
2021-06-25 10:06 ` Walter Harms [this message]
2021-06-25 10:21   ` Pablo Neira Ayuso
2021-07-02  0:56 ` Pablo Neira Ayuso

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