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 A1ACD389E1A; Thu, 17 Sep 2026 18:46:05 +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=1789670766; cv=none; b=MqhYEK0h3fooqPQ6vxqYiefMbh6kSMW0OxB81DhKeYrLYCEfnaUN50IH1Z/5EjrrggOtXuXkxJojrUH3DU/YHyN90fh/V61MUr1I/sw/fSWRTzhIxiX3suCuiRG1z0g9vceiCrWFXWrZbXNZ1NIn9kDrqX+BwWlS1IcTSYzAkGQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789670766; c=relaxed/simple; bh=NsqxIp7uC4YoG2GqX/rLPPXKoNGEKIITPzXy/xN1ig8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CzfTH/KPXFtjHsDk91ZDdrBz0SfCsf7MDrnZ/PULDkxCN8RSArVpjUAbt8ityikvFquXdBcuOmd4U8vnfKBrtz8bkeSjp+BEpZS3Ia8sslHjqu1pbDa6fBg8OHAgIZXqCP/568u72kd6A/zWBTztj8yqqXNXGJzrBSrTv5uG+pQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VnCeRR6w; 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="VnCeRR6w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1B251F000FF; Thu, 17 Sep 2026 18:46:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789670765; bh=WdghF2jvetvFImcRQyolFMF+W5hUzCVSkMsvHa8/r0w=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=VnCeRR6wtFsbDXQFUkQQaRSq+7+fut+fs8H1CRO5TX3yXLBt0jtPdENsqloZVeSMZ OTIBvhekWaF5Vi9SKvFwInzLSDfjbnRRVPxlYp8CxKKYxvfE8vwODINuH6mEa+6Kuf 4NUupDdvAztYJmUYIXyw5vioyS5O8rVn+W5vKrqU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alice Mikityanska , Willem de Bruijn , Willem de Bruijn , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.12 0724/1102] net: ipv6: Clamp to IP6_MAX_MTU in ip6_dst_mtu_maybe_forward Date: Thu, 17 Sep 2026 16:11:07 +0100 Message-ID: <20260917151558.535125188@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151539.408551884@linuxfoundation.org> References: <20260917151539.408551884@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alice Mikityanska [ Upstream commit 199271ebc71c1e0913b2fad988a7bff330a8828a ] Commit 427faee167bc ("net: ipv6: introduce ip6_dst_mtu_maybe_forward") dropped the IP6_MAX_MTU clamp that used to be present in ip6_mtu(). A similar IPv4 commit ac6627a28dbf ("net: ipv4: Consolidate ipv4_mtu and ip_dst_mtu_maybe_forward") preserves the IP_MAX_MTU clamp. Restore the upper bound in the IPv6 flow to avoid potential 16-bit overflows in forwarding paths. Fixes: 427faee167bc ("net: ipv6: introduce ip6_dst_mtu_maybe_forward") Signed-off-by: Alice Mikityanska Suggested-by: Willem de Bruijn Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260901195714.673548-5-alice.kernel@fastmail.im Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- include/net/ip6_route.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h index 59f48ca3abdf5..80f61c76ebc04 100644 --- a/include/net/ip6_route.h +++ b/include/net/ip6_route.h @@ -343,6 +343,8 @@ static inline unsigned int ip6_dst_mtu_maybe_forward(const struct dst_entry *dst rcu_read_unlock(); out: + mtu = min_t(unsigned int, mtu, IP6_MAX_MTU); + return mtu - lwtunnel_headroom(dst->lwtstate, mtu); } -- 2.53.0