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 E776A3112C1; Sat, 30 May 2026 18:07:43 +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=1780164464; cv=none; b=J+RnMyLWdAb6EPqs1+GfziLtcCORk7GIoo1pxwzSiyCWb9VZLTrlDCELyosiQZNKk5DmyStzVIDx/62VRjihJfIn1VsqYaD504ExMobf+U7o7u/NDFGZMRDcZJa+Hjs4Njb13iRar28woLdxFptK47M9W0WG7EDZlkC08FyScW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780164464; c=relaxed/simple; bh=GUJhRvwhEjV4Qdme/cFu5dGliUtos4inbn0uasknNmA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=D2u1APKMnbsDTWDyDSbrH2fn2RLTp0CrbCq4wRqINkNh7cRRV5o4hQwG0QSSKyisODwqTv4cwUkSy9eqwkqKfFaV+YJLpVFoiziUxeojdv8qZj9cFdEkdA0wLzT2Zv7ht0zPZ+QP9RFtsv+cwBAJHgJNzZruCE57MzXp/KSOp0k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=E41eMRs+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="E41eMRs+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED7AB1F00893; Sat, 30 May 2026 18:07:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780164463; bh=nkbfZ/ShXwvoKbBYAt4J9PkVl32WOk2bH2zmcCCFkBw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=E41eMRs+XX+RWtJX1mrWwxLp4mH2+pnvOzKTKQysGiNoWahSSiIVpPP45z44bg6jI Fad/TfDAiZtMpwX193QGD3HChH4LqMyCMvzAQXLwoC8e7Bo/GSUpnTMOYB/+oN9kp1 E4udwoBB68NQ0SEpsfeLf1J5ATDsziTLZc6rRLXs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jiayuan Chen , David Ahern , Paolo Abeni , Sasha Levin Subject: [PATCH 5.15 555/776] nexthop: fix IPv6 route referencing IPv4 nexthop Date: Sat, 30 May 2026 18:04:29 +0200 Message-ID: <20260530160254.490213980@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160240.228940103@linuxfoundation.org> References: <20260530160240.228940103@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiayuan Chen [ Upstream commit 29c95185ba32b621fbc3800fb86e7dc3edf5c2be ] syzbot reported a panic [1] [2]. When an IPv6 nexthop is replaced with an IPv4 nexthop, the has_v4 flag of all groups containing this nexthop is not updated. This is because nh_group_v4_update is only called when replacing AF_INET to AF_INET6, but the reverse direction (AF_INET6 to AF_INET) is missed. This allows a stale has_v4=false to bypass fib6_check_nexthop, causing IPv6 routes to be attached to groups that effectively contain only AF_INET members. Subsequent route lookups then call nexthop_fib6_nh() which returns NULL for the AF_INET member, leading to a NULL pointer dereference. Fix by calling nh_group_v4_update whenever the family changes, not just AF_INET to AF_INET6. Reproducer: # AF_INET6 blackhole ip -6 nexthop add id 1 blackhole # group with has_v4=false ip nexthop add id 100 group 1 # replace with AF_INET (no -6), has_v4 stays false ip nexthop replace id 1 blackhole # pass stale has_v4 check ip -6 route add 2001:db8::/64 nhid 100 # panic ping -6 2001:db8::1 [1] https://syzkaller.appspot.com/bug?id=e17283eb2f8dcf3dd9b47fe6f67a95f71faadad0 [2] https://syzkaller.appspot.com/bug?id=8699b6ae54c9f35837d925686208402949e12ef3 Fixes: 7bf4796dd099 ("nexthops: add support for replace") Signed-off-by: Jiayuan Chen Reviewed-by: David Ahern Link: https://patch.msgid.link/20260413114522.147784-1-jiayuan.chen@linux.dev Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/ipv4/nexthop.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c index 9bd72526000c4..8cd148be09c6b 100644 --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -2161,10 +2161,10 @@ static int replace_nexthop_single(struct net *net, struct nexthop *old, goto err_notify; } - /* When replacing an IPv4 nexthop with an IPv6 nexthop, potentially + /* When replacing a nexthop with one of a different family, potentially * update IPv4 indication in all the groups using the nexthop. */ - if (oldi->family == AF_INET && newi->family == AF_INET6) { + if (oldi->family != newi->family) { list_for_each_entry(nhge, &old->grp_list, nh_list) { struct nexthop *nhp = nhge->nh_parent; struct nh_group *nhg; -- 2.53.0