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 DA9224F5E0E; Wed, 30 Sep 2026 16:57:42 +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=1790787464; cv=none; b=L+WxPaxUWKi+9B9ImKPfxzDOQyYaZaG7W42MRbqspYTFm+ouE1JG//5tNQ4xfWqXfl1F8+8xiE009E1JcpsIcH1bB1M8jytVVN0OgxuNO2Akrp/JwEbHXp2mg03Vji4dihc8bJTDk5FWhfMMA+/3rhNeaKEsfTtv5j+7YJaxtUM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790787464; c=relaxed/simple; bh=NbKpYIxnhh9jlxaApLSbe7QsjNtNq1kAEU7pvyjDWQY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jbOECL+GjTfkeFMmpVRrkFhrgC5wo5Pa+tslpZetCg9/8b4wcnQ1p4Ik7pSspiIxfX5OPT0zKOrOnrqzW2h3xl5yNdE+FECvYzs4xcB4V0IISLua30DPQfxA407N9smYokUmUukOCMfIOYkiWc/YZ7i/rUE/iNuUG+/KT0MIuMU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RuVrT4U8; 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="RuVrT4U8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 378921F000FF; Wed, 30 Sep 2026 16:57:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790787462; bh=hdfnu3/71AZsi6HajML0F7j+6gOraONGPQYi60oXRxU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RuVrT4U8nQygpy323wRHbmW32NOWr1UsfXjEnvruwK4qNnF5NbOvXxdazweA/IMEo Xcpqttf8tlDvOK+7WVcHGG8lOKzjDGtOYGnhcgpnkREZvq650/Z4NtO2Zf/D343Ve0 yJMYC/mg0+4zXK98ezqcQl2Nm34I79c+q/Sb7QRY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, co+0ea1ac045375cf05@bugs.sh, Xiang Mei , Simon Horman , Jakub Kicinski Subject: [PATCH 7.2 238/457] vlan: require the MAC header to be present in __vlan_insert_inner_tag() Date: Wed, 30 Sep 2026 17:25:43 +0200 Message-ID: <20260930152351.180161435@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152346.024115587@linuxfoundation.org> References: <20260930152346.024115587@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: Xiang Mei commit ab888242fce4f16f6c4d4c6ec53939ad36aa3b3a upstream. __vlan_insert_inner_tag() only guarantees head room via skb_cow_head(), never that mac_len bytes of MAC header are present. Its ETH_HLEN wrappers - __vlan_insert_tag() under skb_vlan_push(), and vlan_insert_tag() under validate_xmit_vlan() on the generic transmit path - therefore rewrite the first 16 bytes at skb->data: a 12-byte memmove plus two 2-byte stores at +12 and +14. No caller supplies the bound, while the pop helpers use skb_ensure_writable()/pskb_may_pull(). An IFF_TUN device has hard_header_len == 0, so packet_snd() accepts a one-byte AF_PACKET/SOCK_RAW frame. The first vlan push only sets a hwaccel tag; the next - clsact "action vlan push" or bpf_skb_vlan_push() - enters the helper with skb->len still 1. The head comes from skbuff_small_head without __GFP_ZERO, so each push drags bytes from beyond skb->tail into the frame. After three the one-byte send leaves as 13 bytes carrying 11 bytes of uninitialised slab: 0000: 5a b3 62 12 80 88 ff ff 00 b3 62 12 81 `------------------------------' only 0x5a was sent; the rest is slab, here the top 56 bits of a linear-map address Require the MAC header the helper rewrites to be present, so such a frame is dropped rather than transmitted. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Reported-by: co+0ea1ac045375cf05@bugs.sh Signed-off-by: Xiang Mei Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260915083152.705309-1-xmei5@asu.edu Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- include/linux/if_vlan.h | 3 +++ 1 file changed, 3 insertions(+) --- a/include/linux/if_vlan.h +++ b/include/linux/if_vlan.h @@ -365,6 +365,9 @@ static inline int __vlan_insert_inner_ta const u8 meta_len = mac_len > ETH_TLEN ? skb_metadata_len(skb) : 0; struct vlan_ethhdr *veth; + if (unlikely(!pskb_may_pull(skb, mac_len))) + return -EINVAL; + if (skb_cow_head(skb, meta_len + VLAN_HLEN) < 0) return -ENOMEM;