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 D405836402B; Tue, 6 Jan 2026 17:51:04 +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=1767721864; cv=none; b=Z+M9FGQMXH8jpWHQZm8adRCTj6f3Hh22JU7GqWuboDd58rMqBw7TODEMC+ksaJqohwEYnaoxiS4yBejtWehsGt1vUQzL4R3RBm8lcVfo6Szv6KkUiet/vqF67cI5xOgA2B95ivXyh0gP6mQawqkq5EUzKe8mBzo0ZpqawM3geos= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767721864; c=relaxed/simple; bh=1dooVpSJNOpFVj9jGnzjR7tbuUIeuB7hflP72OlzSdk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dNHufiwAbOb0nu8h6K/nxICTqO0oAB9IMUAbWoPfVrpdyVP36vLQwMp7RVqDVNFaqS/VDbYl4A5VhUR1EyIc7+CyKHQ6aPVVuEuvWLuM97KyNMR4/OMRGr1Sw3/aaH/L98vxFhT6BK1RbV9J8256uDaiQKqJb38yMMV9SQYq2AE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JiOYQeDf; 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="JiOYQeDf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1474DC19423; Tue, 6 Jan 2026 17:51:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767721864; bh=1dooVpSJNOpFVj9jGnzjR7tbuUIeuB7hflP72OlzSdk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JiOYQeDfW+Q6E93gmbuEJW9Xvvy8SGdzJaTpXFLn9pAG79R2+ciC+U4pG67nrrYUn fsMHxkswuYUcAE8DC9V6ZccBWdRMfOD3x3IOhirRFcSdDynMrMqNIHhIOAtvy1tIRl Xj65SAJ9esTEbh7+Q36NwkloBClSkqRiFyMOEXQ0= 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 6.18 061/312] ipv4: Fix reference count leak when using error routes with nexthop objects Date: Tue, 6 Jan 2026 18:02:15 +0100 Message-ID: <20260106170550.057891656@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260106170547.832845344@linuxfoundation.org> References: <20260106170547.832845344@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 6.18-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 59a6f0a9638f..7e2c17fec3fc 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -2053,10 +2053,11 @@ 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