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 53E222690EC; Mon, 9 Feb 2026 14:48:54 +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=1770648534; cv=none; b=UrmZ8f2dtk1P823CgPVHpyQ4BGbZ1uOH6OBebyWh6Fp7eDpzo1mLiZvJayUK5gPOqXvpSUkfiXTIV/Vj86GCtHq4xlACmXjLiF/PjQdIlIlu0zwoiXjc3y48er3qtRM7Fmu01ej9D2T9e9kUcGA75hqTgqY/Gg8wNgrAWwJN2H4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770648534; c=relaxed/simple; bh=ofipjIzMcZPqXhQOgRRP/w+DoOFJF1MxmDBy62Cu378=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=N8G01Xx3MP0wyCSnjzXahR80wHgjpEKHBWfmhItYwWovyAZJYa+UI/uw74v4z82/0SuK+5OEsMfQDnwhhss79Y44+CAeabJJ1yAorKqwKjs+12jbxMuJXcDcq2PO4QJ/mr0hAfNQ/pXNuIshlZ9lzRpHCF6Md701AIsFH9CwoRc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1O+k8oKt; 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="1O+k8oKt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCFD5C116C6; Mon, 9 Feb 2026 14:48:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1770648534; bh=ofipjIzMcZPqXhQOgRRP/w+DoOFJF1MxmDBy62Cu378=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1O+k8oKtOWMz7loBJruWtjKZh7PJ3CdUxhYvBA0cMpo6Kk/smHtR3/aTxiIXDbuRS EcS1eFv1SpoGCU8HXWbb37WDCmMpco/nct/kt5/J5Aql0ZVljRxpqAXkmCZexWZBBl 2AHbNZvAYtnfMMPrLIoMNjXiUG7aGFtnH73jkwzg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , valis , syzbot+7182fbe91e58602ec1fe@syzkaller.appspotmail.com, Boudewijn van der Heide , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6 67/86] macvlan: fix error recovery in macvlan_common_newlink() Date: Mon, 9 Feb 2026 15:24:30 +0100 Message-ID: <20260209142307.188195144@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260209142304.770150175@linuxfoundation.org> References: <20260209142304.770150175@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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit f8db6475a83649689c087a8f52486fcc53e627e9 ] valis provided a nice repro to crash the kernel: ip link add p1 type veth peer p2 ip link set address 00:00:00:00:00:20 dev p1 ip link set up dev p1 ip link set up dev p2 ip link add mv0 link p2 type macvlan mode source ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20 ping -c1 -I p1 1.2.3.4 He also gave a very detailed analysis: The issue is triggered when a new macvlan link is created with MACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or MACVLAN_MACADDR_SET) parameter, lower device already has a macvlan port and register_netdevice() called from macvlan_common_newlink() fails (e.g. because of the invalid link name). In this case macvlan_hash_add_source is called from macvlan_change_sources() / macvlan_common_newlink(): This adds a reference to vlan to the port's vlan_source_hash using macvlan_source_entry. vlan is a pointer to the priv data of the link that is being created. When register_netdevice() fails, the error is returned from macvlan_newlink() to rtnl_newlink_create(): if (ops->newlink) err = ops->newlink(dev, ¶ms, extack); else err = register_netdevice(dev); if (err < 0) { free_netdev(dev); goto out; } and free_netdev() is called, causing a kvfree() on the struct net_device that is still referenced in the source entry attached to the lower device's macvlan port. Now all packets sent on the macvlan port with a matching source mac address will trigger a use-after-free in macvlan_forward_source(). With all that, my fix is to make sure we call macvlan_flush_sources() regardless of @create value whenever "goto destroy_macvlan_port;" path is taken. Many thanks to valis for following up on this issue. Fixes: aa5fd0fb7748 ("driver: macvlan: Destroy new macvlan port if macvlan_common_newlink failed.") Signed-off-by: Eric Dumazet Reported-by: valis Reported-by: syzbot+7182fbe91e58602ec1fe@syzkaller.appspotmail.com Closes: https: //lore.kernel.org/netdev/695fb1e8.050a0220.1c677c.039f.GAE@google.com/T/#u Cc: Boudewijn van der Heide Link: https://patch.msgid.link/20260129204359.632556-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/macvlan.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c index 09db43ce31767..fea7352e2a470 100644 --- a/drivers/net/macvlan.c +++ b/drivers/net/macvlan.c @@ -1572,9 +1572,10 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev, /* the macvlan port may be freed by macvlan_uninit when fail to register. * so we destroy the macvlan port only when it's valid. */ - if (create && macvlan_port_get_rtnl(lowerdev)) { + if (macvlan_port_get_rtnl(lowerdev)) { macvlan_flush_sources(port, vlan); - macvlan_port_destroy(port->dev); + if (create) + macvlan_port_destroy(port->dev); } return err; } -- 2.51.0