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 869EF5111AE for ; Tue, 29 Sep 2026 14:12:44 +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=1790691165; cv=none; b=On/OYpHYCOAEBK4YRshbmCrCIijjUt/hBW7cB9Dg3TFjteLyczzjHNUOkGa4ywl6rznyeKjLNnPcglVyqlTVmktb3UBsGEtwjywsoL6Pl+OtzUCh+RhL6cWQzIN8JLYbCc4YQ7Im3fZujjiCDgfg0OhVHZ3WQ7YoTyJbMhf2JdQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790691165; c=relaxed/simple; bh=agINWrTkL2s4cUvPRd+TAos57xdxeAsbrQFMvF2CSdg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sLzDv4YOuqHeBsrp7lt/tsF+viLIJUSQDTLW380x/SUIcrplh+TFLV/loUlfu0uoiz7gPVnvbTymO4Gk3ADo/0m7ktpYL8UuXKtd81hy45kB2aRfGuYdILCugDvF8Q22xyN5rkzv3tl5uOO5yXZ9BeyCMobMGqlRPZYOEh8HpCM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=e+jnCW1M; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="e+jnCW1M" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C136E1F000FF; Tue, 29 Sep 2026 14:12:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790691164; bh=aiUe78Ey6BvHTXLsLLWnv5+5FCkeJbIuDg+UZSwtuaA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=e+jnCW1MCwKHxelzz52cbLipFvt0J3kM1pB3zdX7XzKdsoadoNE094sHhfFTHOXsv 1Ah0EMJc9KgMFCSMl3RR/MNXzEJ8mcbIx21a/EZ2K2Nm0tN1jLo+iQof3U8j7UTqnn 8Pd7IKavxqOcmzJyLcLqhHL0tx10ASMQGVWfpRYukokIvhH/WpK1JHzbCXAFhdXHbl vmOp9W6TP29KLYi6HMglZrTpA6cZ7FNRX/V8h9GIamZ5QGhVQkBDU1fCnKIBYcM3i8 Zwki1mWIrKNjkAZ4n0/K9et0hLXyL9eLgbEXRmYNLPawCqyZQA+DZIoZJWv2uqHrh+ EUnZP2SdrlMCg== From: Sasha Levin To: stable@vger.kernel.org Cc: Xiang Mei , co+0ea1ac045375cf05@bugs.sh, Simon Horman , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15.y] vlan: require the MAC header to be present in __vlan_insert_inner_tag() Date: Tue, 29 Sep 2026 10:12:42 -0400 Message-ID: <20260929141242.3537639-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026092954-alienable-pointed-d2ff@gregkh> References: <2026092954-alienable-pointed-d2ff@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Xiang Mei [ Upstream commit ab888242fce4f16f6c4d4c6ec53939ad36aa3b3a ] __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 [ adjusted context around skb_cow_head(skb, VLAN_HLEN) because the branch lacks upstream meta_len handling. ] Signed-off-by: Sasha Levin --- include/linux/if_vlan.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h index 3728e3978f833..2759d38466663 100644 --- a/include/linux/if_vlan.h +++ b/include/linux/if_vlan.h @@ -346,6 +346,9 @@ static inline int __vlan_insert_inner_tag(struct sk_buff *skb, { struct vlan_ethhdr *veth; + if (unlikely(!pskb_may_pull(skb, mac_len))) + return -EINVAL; + if (skb_cow_head(skb, VLAN_HLEN) < 0) return -ENOMEM; -- 2.53.0