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 224ED4EFFB8; Thu, 17 Sep 2026 15:42:26 +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=1789659751; cv=none; b=Cn+Wsb4OAswOOZDOnQupoSDnJA2+mlqxeyN3O4gRVWvODy48k/MSs92Upeyqje2TiHFu90alxr4eTNtx53H52uQkeYppJxAyXk04IgMrqmFDQcxvij5pHpXmd0dZMv5s2cYw2n4KNJNdmjOPSh2NVnkqY03cQ0fzkBOKt4S5dYc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789659751; c=relaxed/simple; bh=Q3CcGhTzQ1ahR/M500i4w5W6XfyhzxLNKqP1+KhE8Tg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Bfzw1uAHmHjGionxAAZ4xTqOPTgY+TZt3zJ6CvkgtE6M4lM/GEPvqDT7JFD+JCvvYXXVXsfDVSr+Vmp7lmow7Y6OCTdCiPNDTFq2drKKuhtwrHQFegwgnsHTrW6yYhHw+B+DRlilXdxJ4ohldcMo0upkTYaa9hDqwrTnoxApnnw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vKGnS9zi; 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="vKGnS9zi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4ACC81F00898; Thu, 17 Sep 2026 15:42:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789659743; bh=IWeWtN6+bADMexlZzhbjw8LyhlZTO5qquWhQ9wjzSBM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=vKGnS9zilhiu6t9c4z5Fi+5+0J5AyiS9xW/ih735rO7CnlEBRkPKlEPS/1GuQ697c G3EJl6J5IKdEzC4PcRK3ljUdMc9cCjhbAzHCK9g73jZHe1pmgRz9bMwspH03flT5AK cc6RrtTAj1bvxnDAU0sqU2r1hHNMNzk0YGX/5H58= 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 7.2 358/733] net: ipv6: Clamp to IP6_MAX_MTU in ip6_dst_mtu_maybe_forward Date: Thu, 17 Sep 2026 16:11:06 +0100 Message-ID: <20260917151400.516013417@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@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 7.2-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 ac1acc0b74368..745ab62154ace 100644 --- a/include/net/ip6_route.h +++ b/include/net/ip6_route.h @@ -382,6 +382,8 @@ 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