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 1BF80329C60; Wed, 10 Jun 2026 16:16:42 +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=1781108204; cv=none; b=qLFt5/vHxabLIDii8Pxrs/n8DNRodqtGMtlweJ1644AXtTmfx6Pmsmbgh2L+Sp17yF8pCEMudddnOClM0DKgFcLUk3tXw2S+zVclEUHP+l6Ha6UnQ8GzZVL4MiR1l0G0mxk3Djim8qIk95//GPBHJN2iNQGeoHMtzVIDSXYMSE8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781108204; c=relaxed/simple; bh=GJRjfQuiXWpUPIr64uCDdPcAX/1dVPQXePOUWLcOwkg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BdQzfAjwb5K903R4iiAXy949o7ylI9IrVC68o34gG9t/AnreD2xAraPS+p7R1QUFmjEObxI//OHRw/nQfLvMl8n4f2qXUuTZcrAJGcj3zYCnGnhvblkJ45foyXUiqRJOJIUUQxHCO9OqSNds5ya2h46pXxVIbwpeLkOiaA7/mtQ= 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=Ep9XHFEB; 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="Ep9XHFEB" Received: from localhost.localdomain (mail-agni [217.70.190.124]) by mail.netfilter.org (Postfix) with ESMTPSA id 3228F601C4; Wed, 10 Jun 2026 18:16:41 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org; s=2025; t=1781108201; bh=Q4lYkQsUNFsA2CXE/up+HPNHeR6IxkRrRE3GbvG/Jss=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ep9XHFEBG4GRjxCKbMjCA1nh7XHMQXFhXre2XVgV6dn8MTHk352eYpjdu/xwzUn7t uKMQ1N8fWr3Ebk28QjX47wMwdjauTNA7uYy4kEIi+2os+Lwm4+++Zpg5HJhkV8IL7p 934KYNvE0y4jMCJZB+6H6c8+tmfpfOut6t2QlTyzEKOz18goTAp8MG9M/mSwyyjjSS Q6Dilvdsgcc/ruJXD1onGbS6+fA5vz/9pmRcbV6hGwzqMY2Xk2EVdUANayORmLpp7O FfPNDj9XVIiQy4Sxn9/hdZIO7ZmKnsBzSwFWRakA4zYvcMtHAUR5ueNzKmOLtad+VB YEf6AzpBYAFfg== 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 7/8] netfilter: nft_fib: fix stale stack leak via the OIFNAME register Date: Wed, 10 Jun 2026 18:16:27 +0200 Message-ID: <20260610161629.214092-8-pablo@netfilter.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260610161629.214092-1-pablo@netfilter.org> References: <20260610161629.214092-1-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 From: Davide Ornaghi For NFT_FIB_RESULT_OIFNAME the destination register is declared with len = IFNAMSIZ (four 32-bit registers), but on the lookup-fail, RTN_LOCAL and oif-mismatch paths nft_fib{4,6}_eval() only writes one register via "*dest = 0". The remaining three registers are left as whatever was on the stack in nft_do_chain()'s struct nft_regs, and a downstream expression that loads the register span can leak that uninitialised kernel stack to userspace. The NFTA_FIB_F_PRESENT existence check has the same shape: it is only meaningful for NFT_FIB_RESULT_OIF, yet it was accepted for any result type while the eval stores a single byte via nft_reg_store8(), leaving the rest of the declared span stale. Fix both: - replace the bare "*dest = 0" in the eval with nft_fib_store_result(), which strscpy_pad()s the whole IFNAMSIZ for OIFNAME (and is already used on the other early-return path), and - restrict NFTA_FIB_F_PRESENT to NFT_FIB_RESULT_OIF and declare its destination as a single u8, so the marked span matches the one byte the eval writes. Fixes: f6d0cbcf09c5 ("netfilter: nf_tables: add fib expression") Suggested-by: Florian Westphal Cc: stable@vger.kernel.org Signed-off-by: Davide Ornaghi Signed-off-by: Pablo Neira Ayuso --- net/ipv4/netfilter/nft_fib_ipv4.c | 2 +- net/ipv6/netfilter/nft_fib_ipv6.c | 2 +- net/netfilter/nft_fib.c | 6 ++++++ 3 files changed, 8 insertions(+), 2 deletions(-) diff --git a/net/ipv4/netfilter/nft_fib_ipv4.c b/net/ipv4/netfilter/nft_fib_ipv4.c index 9d0c6d75109b..177d738825b4 100644 --- a/net/ipv4/netfilter/nft_fib_ipv4.c +++ b/net/ipv4/netfilter/nft_fib_ipv4.c @@ -128,7 +128,7 @@ void nft_fib4_eval(const struct nft_expr *expr, struct nft_regs *regs, fl4.saddr = get_saddr(iph->daddr); } - *dest = 0; + nft_fib_store_result(dest, priv, NULL); if (fib_lookup(nft_net(pkt), &fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE)) return; diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c index 2dbe44715df3..b9ad7cac1417 100644 --- a/net/ipv6/netfilter/nft_fib_ipv6.c +++ b/net/ipv6/netfilter/nft_fib_ipv6.c @@ -239,7 +239,7 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs, lookup_flags = nft_fib6_flowi_init(&fl6, priv, pkt, oif, iph); - *dest = 0; + nft_fib_store_result(dest, priv, NULL); ret = nft_fib6_lookup(nft_net(pkt), &fl6, &res, lookup_flags); if (ret || res.fib6_flags & (RTF_REJECT | RTF_ANYCAST | RTF_LOCAL)) return; diff --git a/net/netfilter/nft_fib.c b/net/netfilter/nft_fib.c index 327a5f33659c..a1632e308f18 100644 --- a/net/netfilter/nft_fib.c +++ b/net/netfilter/nft_fib.c @@ -107,6 +107,12 @@ int nft_fib_init(const struct nft_ctx *ctx, const struct nft_expr *expr, return -EINVAL; } + if (priv->flags & NFTA_FIB_F_PRESENT) { + if (priv->result != NFT_FIB_RESULT_OIF) + return -EINVAL; + len = sizeof(u8); + } + err = nft_parse_register_store(ctx, tb[NFTA_FIB_DREG], &priv->dreg, NULL, NFT_DATA_VALUE, len); if (err < 0) -- 2.47.3