From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 7DA3C3DB647 for ; Mon, 15 Jun 2026 13:28:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781530084; cv=none; b=K4YdiEV+XLIUss1gB1L+yewVTvYXfqV1ZwXqpSU5Ihpzbun1XGRV1n9eaOAft1ru4CPHgckd1+IzxSW+OhCNvkp2sCIOZ6wh1vpXDdSXuqFqvUhsEPaSW9BJ395/b55uzPhgtHsJq6dck34+Y0OvPJN/ESZ8I33nHSMN+0r5hgk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781530084; c=relaxed/simple; bh=PYr/P5p9USRlZDfXmQJGLEjgbW2FKXvbtbeGNA4umxo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MFTiUur0lVuuvFqYxWdEHynI/cSoZZkjJaI2odfCta0n9pm6d3FSq/LDBkEF7JwZTvPLSJr9vSa5iXciexiG1TjavuZwG0OIeaS+aHsOJlOVLiT6Wy8/e6pn+1r4+umOFoxPpvlyAakGSne0FW3YONqj55waaiFg1LrYJX2QVXA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NA7vZPhc; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NA7vZPhc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C684C1F000E9; Mon, 15 Jun 2026 13:28:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781530083; bh=TMlDCoYoSrO3vdRyX1vZusXJAZ9OvXBopTNdM5QHveQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NA7vZPhcprmECp59Sso8lwk3t/jd7d2HKwELgzFIPIvqilFkvTcTXpngFV8NXuQ1Z jkZH3vtV08WI+kB865YmUad8QDrW+Vq+vldXIirb47noYJ8l8ZkGYHtwMuagqQm0kw hjZTH04ZnfWaFe4uywhtNMbVDm088qQZIYP5SQ0Urk2wYb8wPIp4Ha5EhriEFN8xCe aqS1CatJKzGOjXs/zwdAAtdpmD8XhXvFO8rD1uKAyBkDHLqtBVZJ5z/H9TK5ATFzoy IlGX1jLAzSLmNZC1TFk/+xMG0SO0S7tgDnhI879VX7tkMMnKfoX/71u0Pltx4kfc96 fDsYoKKBNueEg== From: Sasha Levin To: stable@vger.kernel.org Cc: Davide Ornaghi , Florian Westphal , Pablo Neira Ayuso , Sasha Levin Subject: [PATCH 6.18.y] netfilter: nft_fib: fix stale stack leak via the OIFNAME register Date: Mon, 15 Jun 2026 09:28:01 -0400 Message-ID: <20260615132801.2063529-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026061541-acrobat-user-e460@gregkh> References: <2026061541-acrobat-user-e460@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Davide Ornaghi [ Upstream commit ab185e0c4fb82dfba6fb86f8271e06f931d9c64c ] 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 [ kept the tree's older `ip6_route_lookup()`/`rt6_info` IPv6 context and changed only `*dest = 0;` to `nft_fib_store_result(dest, priv, NULL);` ] Signed-off-by: Sasha Levin --- 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 82af6cd76d13e0..e695283aeb2d04 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 421036a3605b46..3005dfbca6155b 100644 --- a/net/ipv6/netfilter/nft_fib_ipv6.c +++ b/net/ipv6/netfilter/nft_fib_ipv6.c @@ -192,7 +192,7 @@ 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); rt = (void *)ip6_route_lookup(nft_net(pkt), &fl6, pkt->skb, lookup_flags); if (rt->dst.error) diff --git a/net/netfilter/nft_fib.c b/net/netfilter/nft_fib.c index 96e02a83c045e2..22846136c754a2 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) -- 2.53.0