From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 801A72BE7B2; Tue, 6 Jan 2026 17:32:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767720736; cv=none; b=fvp6tRAHmzdYDPF5C9dEfVID7OGDVGrAxqPEZEtSiDYhFIlnd/2J6Q55P1u1SdvWrcWfIDgpH3a8FFCrWGzSEPu6IuxIXQ2Iq0jpiMuPJziYFxZWwxDBrhBHeWxKOzGWylSf2yWmG+g12Mn0RyHCOjn0FtAeKA/mmJm/xuwQj40= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767720736; c=relaxed/simple; bh=6s1i5nMlv5sZhLBpl+CnmKtCxJuwP/mCq8p3s2nuN80=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=H2eIdBdHNCOiOmVIfP2Saluuq05IJ+MZI+voGhhZGDgipGx+cw8kvBE39rMItTz0/aU6qcF1wTfScPZSuvdfgi9mHRI1T9CXwQvMoWRfWPQCq4hYJ9dlOZJrxENf6J614qV5opAOVHvAdnZLf1494Xv5McQOGRL3sVgoED6rnhQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1/OcWM67; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1/OcWM67" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E22C1C116C6; Tue, 6 Jan 2026 17:32:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767720736; bh=6s1i5nMlv5sZhLBpl+CnmKtCxJuwP/mCq8p3s2nuN80=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1/OcWM67pb60z5o1xUzCWd4F+QOeFnHrdDVEJILvzxlaiM5E2rLWLekhWgczxhAmd ZWolNvnuf7kLiB2kXht01DYhiMlV86U3gDF1eoW0yrcX9FqD4D/lXuHsWHM7BHSV8p /NzCwwmEDZO0hMNZTmP/7hRfl6wykOm6nFsv0kYo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tetsuo Handa , syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com, Ido Schimmel , David Ahern , Paolo Abeni , Sasha Levin Subject: [PATCH 6.12 327/567] ipv4: Fix reference count leak when using error routes with nexthop objects Date: Tue, 6 Jan 2026 18:01:49 +0100 Message-ID: <20260106170503.420716141@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260106170451.332875001@linuxfoundation.org> References: <20260106170451.332875001@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ido Schimmel [ Upstream commit ac782f4e3bfcde145b8a7f8af31d9422d94d172a ] When a nexthop object is deleted, it is marked as dead and then fib_table_flush() is called to flush all the routes that are using the dead nexthop. The current logic in fib_table_flush() is to only flush error routes (e.g., blackhole) when it is called as part of network namespace dismantle (i.e., with flush_all=true). Therefore, error routes are not flushed when their nexthop object is deleted: # ip link add name dummy1 up type dummy # ip nexthop add id 1 dev dummy1 # ip route add 198.51.100.1/32 nhid 1 # ip route add blackhole 198.51.100.2/32 nhid 1 # ip nexthop del id 1 # ip route show blackhole 198.51.100.2 nhid 1 dev dummy1 As such, they keep holding a reference on the nexthop object which in turn holds a reference on the nexthop device, resulting in a reference count leak: # ip link del dev dummy1 [ 70.516258] unregister_netdevice: waiting for dummy1 to become free. Usage count = 2 Fix by flushing error routes when their nexthop is marked as dead. IPv6 does not suffer from this problem. Fixes: 493ced1ac47c ("ipv4: Allow routes to use nexthop objects") Reported-by: Tetsuo Handa Closes: https://lore.kernel.org/netdev/d943f806-4da6-4970-ac28-b9373b0e63ac@I-love.SAKURA.ne.jp/ Reported-by: syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com Signed-off-by: Ido Schimmel Reviewed-by: David Ahern Link: https://patch.msgid.link/20251221144829.197694-1-idosch@nvidia.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/ipv4/fib_trie.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index cc86031d2050..658f26d9a9ec 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -2059,10 +2059,11 @@ int fib_table_flush(struct net *net, struct fib_table *tb, bool flush_all) continue; } - /* Do not flush error routes if network namespace is - * not being dismantled + /* When not flushing the entire table, skip error + * routes that are not marked for deletion. */ - if (!flush_all && fib_props[fa->fa_type].error) { + if (!flush_all && fib_props[fa->fa_type].error && + !(fi->fib_flags & RTNH_F_DEAD)) { slen = fa->fa_slen; continue; } -- 2.51.0