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 989A433F8B2; Sat, 17 Oct 2026 15:56:02 +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=1792252563; cv=none; b=JfW/eqoEH8vryVmWB+btzhL6hf8iC88u0oKEnVZikSbXw50mc/9/8moTqG4OqRiNDcBZV0AI3tL20H1rXFLe0UOpfuyvT7PfOJNFMIrBMdvBRCY8T1vff4OKSUUnPR0+qDCm/dUqFjamvAUM5oKOsfu7+6jxJgKyicgTzls5mi8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792252563; c=relaxed/simple; bh=DdZ+wps4VeLxWFrpO06sZjgI4nx56Nhszk2o+0IikA8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=P+I4UoDh4Jrrpa2b0fzgDPhCTffKx+PS9EqfPjYfRVipZ4e2qxDVQKIAXw3bqkmdwscPMuzS6cu9Qc2GjVpKaPXZmH+VAQlKRnkBcfcB1vFQ+2UJwGdueaLtOwHgdFAPaTqpyBCBrM6VVdzPzustsvUYNNoM7u4nj+4f3GDEBtU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=T41dQ3ZN; 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="T41dQ3ZN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E50E51F000C4; Sat, 17 Oct 2026 15:56:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792252562; bh=iOelVktn/joah7pc0hpEe3otRbHcb47DPzveguEvppU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=T41dQ3ZNjKa3sr8jdNasVc0jwmm3RaHyMUO4NDSXZBoiIqQ+ljp3y68NIqdneWI3z WiKdNiOcKtE0W4OTh91F2I7FlTTodmZoV3PGhzmuRoVvXZoUusSzLmp7NtcsOnUDMl Y+zBUPQW0i+BY5mCz8M5edseb1JWpJJClM5wvMWw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ido Schimmel , Daehyeon Ko <4ncienth@gmail.com>, Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 06/52] ip6_gre: remove obsolete ERSPAN PMTU update Date: Sat, 17 Oct 2026 17:54:07 +0200 Message-ID: <20261017155105.052565551@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017155104.830766652@linuxfoundation.org> References: <20261017155104.830766652@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daehyeon Ko <4ncienth@gmail.com> [ Upstream commit 8bc60db48e8cba35488bbd6e1f94aa990afa275a ] A tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb, and mirred can redirect it to a native ip6erspan device. The legacy PMTU update in ip6erspan_tunnel_xmit() treats that metadata dst as a route. Since it has no output device, dst_dev(dst)->mtu dereferences NULL. On v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used self-created user and network namespaces to trigger: KASAN: null-ptr-deref RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0 Kernel panic - not syncing: Fatal exception in interrupt The update is obsolete. Commit fe1a4ca0a2b7 ("ip6_gre: process toobig in a better way") changed IPv6 GRE Too Big handling to update the underlay route and removed the equivalent block from __gre6_xmit(). ip6_tnl_xmit() then propagates the underlay PMTU to the overlay route. Remove the stale ERSPAN copy and its now-unused dst variable. This eliminates the metadata-dst dereference and keeps ERSPAN aligned with IPv6 GRE PMTU handling. Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support") Cc: stable@vger.kernel.org Suggested-by: Ido Schimmel Signed-off-by: Daehyeon Ko <4ncienth@gmail.com> Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20261002033058.358137-1-4ncienth@gmail.com Signed-off-by: Jakub Kicinski [ sashal: Adjusted the deletion to match dst6_mtu() instead of dst_mtu(). ] Signed-off-by: Sasha Levin --- net/ipv6/ip6_gre.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index ebd0198458cd3..e3aedef13ceed 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -922,7 +922,6 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb, { struct ip_tunnel_info *tun_info = NULL; struct ip6_tnl *t = netdev_priv(dev); - struct dst_entry *dst = skb_dst(skb); IP_TUNNEL_DECLARE_FLAGS(flags) = { }; bool truncate = false; int encap_limit = -1; @@ -1058,12 +1057,6 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb, gre_build_header(skb, 8, flags, proto, 0, htonl(atomic_fetch_inc(&t->o_seqno))); - /* TooBig packet may have updated dst->dev's mtu */ - if (!t->parms.collect_md && dst) { - mtu = READ_ONCE(dst_dev(dst)->mtu); - if (dst6_mtu(dst) > mtu) - dst->ops->update_pmtu(dst, NULL, skb, mtu, false); - } err = ip6_tnl_xmit(skb, dev, dsfield, &fl6, encap_limit, &mtu, NEXTHDR_GRE); if (err != 0) { -- 2.53.0