From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.netfilter.org (mail.netfilter.org [217.70.190.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AC8143F8E1F; Wed, 1 Apr 2026 10:37:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.190.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775039828; cv=none; b=DxZ3PHAZEw6X0b4BgWkKKyohCJ8LcjZim4mYrRjeAlcVJ1uDpeANXUbvEvX5zjy+kdReHgvTPVNmlAZEAcYs3mnl4Q+LJtfVa3gqLDpg5jrPV4Z35NFGw3+npT5xaMfhQDbY+xhoZ/LFiceHAgtAWZB5/XXqCu7McBcMtxbacGs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775039828; c=relaxed/simple; bh=CzPSJapt1DbwA+j0vgoQk9f9m0ONreQaBAqQO7KtdMQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gwxZkVToIEFkSR0APq9uhJDnh3+0JwNskAKawtQ2UAIW+XcXOBUw6wEfVgpn2xoGmQLvVEIQz9NLRRNwJjTwfDVSWNgrEwSbhdFDvxvkOED0bNzIQnBO3dUuUPasLhAqD+4+AR/277WE3aiSvSsWRt29IhGiycBLONkmAm+VBGo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=netfilter.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b=GLavjX85; arc=none smtp.client-ip=217.70.190.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=netfilter.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b="GLavjX85" Received: from localhost.localdomain (mail-agni [217.70.190.124]) by mail.netfilter.org (Postfix) with ESMTPSA id 5DBE860275; Wed, 1 Apr 2026 12:37:03 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org; s=2025; t=1775039823; bh=GJuux1UkH0MYTO5Mrxr7dQYCFODMTuquZ2nsGDGYy2U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GLavjX857fZp3WE4GM4L0/Gh9qPWBsecxbQMILd0peYwnMmTd79xMGxx5VUZVLsyC rnC0sbnKZAWFGRro9pnonrTPy3vvOOhVZU/HmQHMr4UUAa4CKyZFl4Tzx7NhvPzpK2 jTvdDe3H9/yei55IweXo7ltpPcqJZxQ4vmxHhA3ajZ1QFpyphG5jISLrTkSLrpv5+L c1WJZQ3+DFYrrKFyN0crSnCOZxIh6yBCmcsxyBO4dxI4JRpTT55rgxCgtoroFeXINs sv3bui4hnA/vVZim106Dl7czZ0FTTMdgU0gMompS2C3vIJr9S9dFreerAWS5GD0uQf Z8gNnQUeR5pGA== From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com, fw@strlen.de, horms@kernel.org Subject: [PATCH net 09/10] netfilter: x_tables: restrict xt_check_match/xt_check_target extensions for NFPROTO_ARP Date: Wed, 1 Apr 2026 12:36:45 +0200 Message-ID: <20260401103646.1015423-10-pablo@netfilter.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260401103646.1015423-1-pablo@netfilter.org> References: <20260401103646.1015423-1-pablo@netfilter.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Weiming Shi says: xt_match and xt_target structs registered with NFPROTO_UNSPEC can be loaded by any protocol family through nft_compat. When such a match/target sets .hooks to restrict which hooks it may run on, the bitmask uses NF_INET_* constants. This is only correct for families whose hook layout matches NF_INET_*: IPv4, IPv6, INET, and bridge all share the same five hooks (PRE_ROUTING ... POST_ROUTING). ARP only has three hooks (IN=0, OUT=1, FORWARD=2) with different semantics. Because NF_ARP_OUT == 1 == NF_INET_LOCAL_IN, the .hooks validation silently passes for the wrong reasons, allowing matches to run on ARP chains where the hook assumptions (e.g. state->in being set on input hooks) do not hold. This leads to NULL pointer dereferences; xt_devgroup is one concrete example: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000044: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000220-0x0000000000000227] RIP: 0010:devgroup_mt+0xff/0x350 Call Trace: nft_match_eval (net/netfilter/nft_compat.c:407) nft_do_chain (net/netfilter/nf_tables_core.c:285) nft_do_chain_arp (net/netfilter/nft_chain_filter.c:61) nf_hook_slow (net/netfilter/core.c:623) arp_xmit (net/ipv4/arp.c:666) Kernel panic - not syncing: Fatal exception in interrupt Fix it by restricting arptables to NFPROTO_ARP extensions only. Note that arptables-legacy only supports: - arpt_CLASSIFY - arpt_mangle - arpt_MARK that provide explicit NFPROTO_ARP match/target declarations. Fixes: 9291747f118d ("netfilter: xtables: add device group match") Reported-by: Xiang Mei Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/x_tables.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index e594b3b7ad82..b39017c80548 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -501,6 +501,17 @@ int xt_check_match(struct xt_mtchk_param *par, par->match->table, par->table); return -EINVAL; } + + /* NFPROTO_UNSPEC implies NF_INET_* hooks which do not overlap with + * NF_ARP_IN,OUT,FORWARD, allow explicit extensions with NFPROTO_ARP + * support. + */ + if (par->family == NFPROTO_ARP && + par->match->family != NFPROTO_ARP) { + pr_info_ratelimited("%s_tables: %s match: not valid for this family\n", + xt_prefix[par->family], par->match->name); + return -EINVAL; + } if (par->match->hooks && (par->hook_mask & ~par->match->hooks) != 0) { char used[64], allow[64]; @@ -1016,6 +1027,18 @@ int xt_check_target(struct xt_tgchk_param *par, par->target->table, par->table); return -EINVAL; } + + /* NFPROTO_UNSPEC implies NF_INET_* hooks which do not overlap with + * NF_ARP_IN,OUT,FORWARD, allow explicit extensions with NFPROTO_ARP + * support. + */ + if (par->family == NFPROTO_ARP && + par->target->family != NFPROTO_ARP) { + pr_info_ratelimited("%s_tables: %s target: not valid for this family\n", + xt_prefix[par->family], par->target->name); + return -EINVAL; + } + if (par->target->hooks && (par->hook_mask & ~par->target->hooks) != 0) { char used[64], allow[64]; -- 2.47.3