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 08754522EE4; Thu, 17 Sep 2026 17:25:23 +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=1789665924; cv=none; b=d+7HqamZMmbRYALDJSvjSmiykZ/xoe0J1vYeTSjCSHku1ieirBSjJPDSM9tbrdjKT3JnA48nx09BDhOeugUqYpF2yI9ksGB0h0kgM4JHusYj1hR0nwWdIInRbaZsYGCJU/LohMI/x0+g8T+PLO0hbfdataWr2QvHW9OhaImK0PA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789665924; c=relaxed/simple; bh=KShLQ7rxuQUOo3swQXdfredMegxVyyeJvtAR12DZOnw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lM8lzr+ADaWcSLRTjCCzFzXDklv4zcbdsYrQPT86vRIMP9nP1h0OkroNWmdXTDxC08VSc8AvTKGxE2ViXohZ/yUYNcbe7AKy73zUoCgkyyviA50j8m0ZWkJRw18g+/QagJ90BhxBUvrK80YDiOwoxIdvtdHFJJaDZC/y7CVVrbM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ESNVl9i1; 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="ESNVl9i1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4EBDB1F00893; Thu, 17 Sep 2026 17:25:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789665922; bh=oeLrcaCsLfg3Nf24ervW0yCUp6U5v6PAYTyasw6+8Ck=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ESNVl9i1MjxtYGJuZTl1v7NR9nGXwoWLWvRv+ERxS1B/P3WMug+ZXpWrku4pgtYGY t7XLPuhmx270uCpmam+yNKG8rvBOeJwMKSziXB3ScTmxJgyQJ8Iy4lgCxFiI2M56i7 JBzNnXwij5H8rnceO8+sMWSS9DCOZdC3jivUb9aA= 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 6.18 0866/1250] net: ipv6: Clamp to IP6_MAX_MTU in ip6_dst_mtu_maybe_forward Date: Thu, 17 Sep 2026 16:11:01 +0100 Message-ID: <20260917151615.446936479@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151551.901433442@linuxfoundation.org> References: <20260917151551.901433442@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: 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 bcbd5eb1a0787..2e8ca123d1465 100644 --- a/include/net/ip6_route.h +++ b/include/net/ip6_route.h @@ -349,6 +349,8 @@ 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