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 B507C4071DA; Sun, 7 Jun 2026 10:19:07 +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=1780827548; cv=none; b=WSaO/f0tkMHOI6xcZUqnO8/qt673ccjw+soBxHu/mvdvVlJd+F90KNHHDNNfpVwXD13CC2DrYSvVQx/O53hjJpDW35jk/YV8nJ/yh/mpyzm07tbrDFeeu0jjTdQbVybrx4EStT1XTBfPnpMUg4A5YNd6rXG5kHzNRym6URqSpAE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780827548; c=relaxed/simple; bh=3nFvpTHymWvvnZtk2fwSSZEQ7d7jVeNaFSZyjBzWawY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=t6sg4GsGbBgBXgO9voL+LkPYEKkEBxurGphh4HhXWofq4YOhNZWBsu5qXp+VcmFrF3sQTBHQxI6XD92LN1aV5m+kgIz18jOlbBe5MTqj/DeuLswYueizplbUowrFQFXB7pbFU/vDGI90rWkc8Cx2glj8h/2XHrkUXy13ehjdlJU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CdTjZsvT; 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="CdTjZsvT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCFAB1F00893; Sun, 7 Jun 2026 10:19:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780827547; bh=VPYAHMgKuRYSVP/Q3dDjE9lpyZ5HMqRoM/SKstxJ9oI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=CdTjZsvT18lWsoNEMCs06PO63AOVrEXhP+qisSJ2QGVNfA9vHE+m9lBdeRkEb4BUy bUJMyxDZTKt+Oai2fh+W3AziL7TF8veLfY3ubL4GmX9SvEnRwCtm3InR1TndK2DPTw MJ141qUxRTBwsVKeQgzp+F2ECtXUQqh2DnDeD4w4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , Stefano Brivio , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 054/315] tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]() Date: Sun, 7 Jun 2026 11:57:21 +0200 Message-ID: <20260607095729.588733314@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260607095727.528828913@linuxfoundation.org> References: <20260607095727.528828913@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: Eric Dumazet [ Upstream commit b4bc94353050b1fa7b702bd4c6600710dd926cff ] Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr() before an skb_cow() call which can reallocate skb->head. Fix this possible UAF by initializing the local variables after the skb_cow() call. Remove skb_reset_network_header() calls which were not needed. Fixes: 4cb47a8644cc ("tunnels: PMTU discovery support for directly bridged IP packets") Signed-off-by: Eric Dumazet Reviewed-by: Stefano Brivio Link: https://patch.msgid.link/20260525201335.2361845-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv4/ip_tunnel_core.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c index 5683c328990f49..d5a63155a05597 100644 --- a/net/ipv4/ip_tunnel_core.c +++ b/net/ipv4/ip_tunnel_core.c @@ -212,7 +212,7 @@ EXPORT_SYMBOL_GPL(iptunnel_handle_offloads); */ static int iptunnel_pmtud_build_icmp(struct sk_buff *skb, int mtu) { - const struct iphdr *iph = ip_hdr(skb); + const struct iphdr *iph; struct icmphdr *icmph; struct iphdr *niph; struct ethhdr eh; @@ -226,7 +226,6 @@ static int iptunnel_pmtud_build_icmp(struct sk_buff *skb, int mtu) skb_copy_bits(skb, skb_mac_offset(skb), &eh, ETH_HLEN); pskb_pull(skb, ETH_HLEN); - skb_reset_network_header(skb); err = pskb_trim(skb, 576 - sizeof(*niph) - sizeof(*icmph)); if (err) @@ -236,7 +235,7 @@ static int iptunnel_pmtud_build_icmp(struct sk_buff *skb, int mtu) err = skb_cow(skb, sizeof(*niph) + sizeof(*icmph) + ETH_HLEN); if (err) return err; - + iph = ip_hdr(skb); icmph = skb_push(skb, sizeof(*icmph)); *icmph = (struct icmphdr) { .type = ICMP_DEST_UNREACH, @@ -308,7 +307,7 @@ static int iptunnel_pmtud_check_icmp(struct sk_buff *skb, int mtu) */ static int iptunnel_pmtud_build_icmpv6(struct sk_buff *skb, int mtu) { - const struct ipv6hdr *ip6h = ipv6_hdr(skb); + const struct ipv6hdr *ip6h; struct icmp6hdr *icmp6h; struct ipv6hdr *nip6h; struct ethhdr eh; @@ -323,7 +322,6 @@ static int iptunnel_pmtud_build_icmpv6(struct sk_buff *skb, int mtu) skb_copy_bits(skb, skb_mac_offset(skb), &eh, ETH_HLEN); pskb_pull(skb, ETH_HLEN); - skb_reset_network_header(skb); err = pskb_trim(skb, IPV6_MIN_MTU - sizeof(*nip6h) - sizeof(*icmp6h)); if (err) @@ -334,6 +332,7 @@ static int iptunnel_pmtud_build_icmpv6(struct sk_buff *skb, int mtu) if (err) return err; + ip6h = ipv6_hdr(skb); icmp6h = skb_push(skb, sizeof(*icmp6h)); *icmp6h = (struct icmp6hdr) { .icmp6_type = ICMPV6_PKT_TOOBIG, -- 2.53.0