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 0F6703C4551; Wed, 30 Sep 2026 19:09:42 +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=1790795383; cv=none; b=F9of9zao0gupWVPGJxFsvaujyYcQfoUeepZpwv3/8qVXltvVaaqEMv4MtoQ4EIfBZka19MaAsnM449fgq1UE3ffDtkUhCpEk/PXnxISexbxrK/7PJg7IbjMmWD/fljdruOaxLhB/eXKFqqIyO8LqQWjhXthAXmx2v0Xbwd7sHqs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790795383; c=relaxed/simple; bh=hMfhcfxRNn6oGAe95/y4sw6jyqIuG9W7ui6PDAvgrvU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=F3n43e4zhSPWkqD8kRqodZ0S6SOK5bV91IUEns8xoaZBPHdlVCHWzjAv3w2YbtV9HVpYIdq3O3dzQwCG/UCCoHeEXhE5+bdxobm2OXEkO+P7qh7mnGJSJcwb9GjdSugXjspUuVcRz0VJJ7dYibqmS/5919ZDwvOiyC5Sesggai4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rxDCGVc5; 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="rxDCGVc5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 651041F000FF; Wed, 30 Sep 2026 19:09:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790795382; bh=4YMmJkfBVbQtPHHNvHAN986+B2vv9z3tMBIFex2OgEM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=rxDCGVc5KlzpVgaAd6tD5Bj+eBny88Fn7oZ5kZpM+B0ql9R6z7/J9oqDVC43nMGuv hmZ3i9ufMLQcwgnqEVUXupEKCN74eWA+6rhErkO32oqqYDmUcgmNeNfOM7P5yoD4Zs mzEapzve3r7IBkWTZbBd2T0KVyVa1Y0s+QX74NhQ= 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 6.6 0542/1193] net: ipv6: Clamp to IP6_MAX_MTU in ip6_dst_mtu_maybe_forward Date: Wed, 30 Sep 2026 17:20:26 +0200 Message-ID: <20260930152446.268127115@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152434.301151190@linuxfoundation.org> References: <20260930152434.301151190@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 6.6-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 392232fcd703c..211d1ef8ab421 100644 --- a/include/net/ip6_route.h +++ b/include/net/ip6_route.h @@ -339,6 +339,8 @@ 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