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 E062440FDB6 for ; Mon, 15 Jun 2026 17:37:20 +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=1781545041; cv=none; b=iXq8PkCaBBSQgR8HsRXYltWsDwabZaAJnoF/Ay7HLHbywFR5RYDXGtsEowj2LyJcdnhPWUm9xzjb9pNVDGbMpElPmqBXy4PgX6rR6vht5LGARHDdVUtuBZ7usoGPALELmL3m9yD7VKdDMQcntbtJnupcwOr5PXTBXpwrukl+VXk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781545041; c=relaxed/simple; bh=zz23/PweprY6M6EdKHWBG6eAfqhkGOk82FJviZpKkWg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QgF8uz+FMUBR21IQxtTY06GaRpEzUWXrjFCptICpuZgVhA1IcHqgcGK5BS2wG4sBp/V+N+wgcoVagvdYnJ7jHFgHO0PMA/j38uNw9sfK6cIu6Vnj3kb4oFtqvD5GYNGzL2pWForAztQmh6FTtE8/L6oLz6D/iKCD7aSJhyS6mQQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DqO7iN6h; 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="DqO7iN6h" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E64261F000E9; Mon, 15 Jun 2026 17:37:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781545040; bh=LV3G/yHeHozmnHhkcEMAzksakmjXxAfXrxtfLWo5Rfc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DqO7iN6hzo4hmduIcN3Cv1XfMUaGf+pv795z7KEPnkEpDiIay9ocJytENak7H8Y2c ovgcEBf8wyL/yyP1UyJ1v+HgL09hbTxjk41JPToxMpkuqGaCBYGsW45O1pJxcfhsjC VFHzGkDx99L/neORtfSYuNc1QWBTqUvN2MSzCAGgCrIsHSk0w6TQIIh/+wIdyyZBKY NGpbefwmVVpfF1T/BK/BVW6e9yrSxajuK9AoNyxX0ljTw0xX2zXyG/EqaCn9Lc6YMl /8Lcg/AGRTaM/AeA5Ex+DdJW+2pohdgMcj2iZCS4czrF3yNRkLO2xE1A1MnwgKIJXU caGFWQQy4aowA== From: Sasha Levin To: stable@vger.kernel.org Cc: Davide Ornaghi , Florian Westphal , Pablo Neira Ayuso , Sasha Levin Subject: [PATCH 5.15.y] netfilter: nft_fib: fix stale stack leak via the OIFNAME register Date: Mon, 15 Jun 2026 13:37:18 -0400 Message-ID: <20260615173718.2302669-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026061544-juicy-dispatch-14c9@gregkh> References: <2026061544-juicy-dispatch-14c9@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 existing `ip6_route_lookup`/`rt6_info` machinery (missing `fib6_lookup` refactor) 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 273b64e3f2f926..37d948d64f77c8 100644 --- a/net/ipv4/netfilter/nft_fib_ipv4.c +++ b/net/ipv4/netfilter/nft_fib_ipv4.c @@ -118,7 +118,7 @@ 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 b7e543d4d57be3..a8343877fdf7fd 100644 --- a/net/ipv6/netfilter/nft_fib_ipv6.c +++ b/net/ipv6/netfilter/nft_fib_ipv6.c @@ -189,7 +189,7 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs, } } - *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 1fd4b2054e8f75..6b4dc8d9eb6794 100644 --- a/net/netfilter/nft_fib.c +++ b/net/netfilter/nft_fib.c @@ -105,6 +105,12 @@ 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