From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792774274; b=vPkh0Ma0FW6+QokwgjRvBZZgcM3uOBZtRMAEe8skaQvuLH9eZfqps05lsIApPc8MnRvO S+/KRPsqM8Ro7TUQowfMerUGbIA+0gsM5ZveGzxyHs49BhaUWqEBKF+GXbbad31nAfva3 gWPTEpZ6+cWHDEUP65k/365+wTnnAI4g1Bb7+ezc71BKHvvJx6vtiG1oOaq0kkyc9X5WV ZqFFbuCmuq4cp1oMh4WBumm8TNkdjWQnhsAvcJJGNKozExfHhhadU8PE+gMnlJh4F6s1D cxmGMYgxj1FNcUTocpTsWwIKU6L3Rk8xjzQ/3RBwsDBfQttS/KVl9ddLKTVPEzWti5Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792774274; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=h6Kj73X5+o7AYjOsr5NiUZPF/hM5I/W6W4D0TR7QUcE=; b=1uGlNcqLYYOEe/66OLNsfx9exDWIevZpLBXpnZPDIfrsUT0PD6c1gYdPR33maReEeinG b3X8nBW3FHsCdU8afex63mB4sJD5Fe1+tgQjStHQTyXmG3opeKt9X4MK096tThmxtyD2l ddAvUnHYk1Dr8eW0vqxoPo5hIY3y2VlvqvzUExXQRLLaJh60O9S3AbrNbNAF+th+cBMpR PBtBaHnVZAAImBG+TXDdw+sP1/IUaCRVVJ6c32Qv2IclnZjBdRP8Ew0JkkSIkPL0BBht7 otDTfgdNQjgu6qMfyXZiYsUQwOuVVTJDpcsLeBNZuwe0N73U1WSp8xJSUoczoILPlyA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b="Cq/wo0WV"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AE67D606A31B; Fri, 23 Oct 2026 16:51:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=Cq/wo0WV Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04D9C1F01825; Fri, 23 Oct 2026 16:51:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792774273; bh=h6Kj73X5+o7AYjOsr5NiUZPF/hM5I/W6W4D0TR7QUcE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Cq/wo0WVUXouqqjfReESMEE61R+QnVsShk8V1bh4wFpsSb5x63+7+X5bCRdxPhTvL ROW22gF1naSVm+ga2xDj1ZgZ6Vl760fhfFEmjzh5KNNx6Aq2B3IP71PpgGZ6jXt+xR 0uGbDK/smL82ns7om0i8ef4gPLCanZCQWqGi4O1I= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vega , Zihan Xi , Eric Dumazet , Ido Schimmel , Jakub Kicinski Subject: [PATCH 6.18 141/193] ipv4: avoid divide by zero in fib_rebalance Date: Fri, 23 Oct 2026 18:36:58 +0200 Message-ID: <20261023163717.541854402@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261023163714.201276352@linuxfoundation.org> References: <20261023163714.201276352@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zihan Xi commit 5046d2880fec7d49ebed2fd2866747ee1d06ad71 upstream. fib_rebalance() computes the total eligible nexthop weight in one pass and programs upper bounds in a second pass. A concurrent change to ignore_routes_with_linkdown can make the first pass return zero while the second pass sees an eligible nexthop, resulting in division by zero. If the first pass reports a zero total, set each nexthop upper bound to -1 and skip the division. This matches the IPv6 fix in commit d2c26c2911dd ("ipv6: avoid divide by zero in rt6_multipath_rebalance") and preserves the lock-free rebalance path. Fixes: 0e884c78ee19 ("ipv4: L3 hash-based multipath") Cc: stable@vger.kernel.org Reported-by: Vega Signed-off-by: Zihan Xi Reviewed-by: Eric Dumazet Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260827182514.4667-2-zihanx@nebusec.ai Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv4/fib_semantics.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -881,7 +881,7 @@ static void fib_rebalance(struct fib_inf change_nexthops(fi) { int upper_bound; - if (nexthop_nh->fib_nh_flags & RTNH_F_DEAD) { + if (!total || nexthop_nh->fib_nh_flags & RTNH_F_DEAD) { upper_bound = -1; } else if (ip_ignore_linkdown(nexthop_nh->fib_nh_dev) && nexthop_nh->fib_nh_flags & RTNH_F_LINKDOWN) {