From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2236DC46467 for ; Tue, 20 Dec 2022 00:47:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232726AbiLTArJ (ORCPT ); Mon, 19 Dec 2022 19:47:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35710 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229477AbiLTArI (ORCPT ); Mon, 19 Dec 2022 19:47:08 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 044FFDF8C; Mon, 19 Dec 2022 16:47:08 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 86E9B61166; Tue, 20 Dec 2022 00:47:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 89814C433F0; Tue, 20 Dec 2022 00:47:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1671497226; bh=bd2xDZMGKClu9pB0PLW4rTKBrXiSlJjJNAS+REMWbe8=; h=From:To:Cc:Subject:Date:From; b=OBSnvldohsaH2riZWNyeuK+gyQf91MBX5bJ8vtEnRlOg+2V/jdI8uFxucwuh0xoaz q/sNEhqrEw37e+/rk0uSJf503XA2NyzmEQfxcHXKAlh6IKXio216sg16/CMA1Xib9H jhwT8dHxZnvU8AHNAn4oq5rZ5aOFdyRCG0Q8beVKxgvDLHK6rO38geU7LmRrct1nPG vtfTVi+t5JszevGLwSh8ivMMZQFu1Za88t+9VZ052yqK8deagkEGBBVHcSbCBlxsPq yJTk/qFEcqR+3qFY+w2Zic/OS4dNQiu7n1RNAKAzsdTNNdiLuW0esDWmCj5CeI8CYQ YGD4hpmUDdG2w== From: Jakub Kicinski To: daniel@iogearbox.net Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, Jakub Kicinski , Anand Parthasarathy , martin.lau@linux.dev, song@kernel.org, john.fastabend@gmail.com, sdf@google.com Subject: [PATCH bpf 1/2] bpf: pull before calling skb_postpull_rcsum() Date: Mon, 19 Dec 2022 16:47:00 -0800 Message-Id: <20221220004701.402165-1-kuba@kernel.org> X-Mailer: git-send-email 2.38.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Anand hit a BUG() when pulling off headers on egress to a SW tunnel. We get to skb_checksum_help() with an invalid checksum offset (commit d7ea0d9df2a6 ("net: remove two BUG() from skb_checksum_help()") converted those BUGs to WARN_ONs()). He points out oddness in how skb_postpull_rcsum() gets used. Indeed looks like we should pull before "postpull", otherwise the CHECKSUM_PARTIAL fixup from skb_postpull_rcsum() will not be able to do its job: if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_start_offset(skb) < 0) skb->ip_summed = CHECKSUM_NONE; Reported-by: Anand Parthasarathy Fixes: 6578171a7ff0 ("bpf: add bpf_skb_change_proto helper") Signed-off-by: Jakub Kicinski --- CC: daniel@iogearbox.net CC: martin.lau@linux.dev CC: song@kernel.org CC: john.fastabend@gmail.com CC: sdf@google.com CC: bpf@vger.kernel.org --- net/core/filter.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 929358677183..43cc1fe58a2c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3180,15 +3180,18 @@ static int bpf_skb_generic_push(struct sk_buff *skb, u32 off, u32 len) static int bpf_skb_generic_pop(struct sk_buff *skb, u32 off, u32 len) { + void *old_data; + /* skb_ensure_writable() is not needed here, as we're * already working on an uncloned skb. */ if (unlikely(!pskb_may_pull(skb, off + len))) return -ENOMEM; - skb_postpull_rcsum(skb, skb->data + off, len); - memmove(skb->data + len, skb->data, off); + old_data = skb->data; __skb_pull(skb, len); + skb_postpull_rcsum(skb, old_data + off, len); + memmove(skb->data, old_data, off); return 0; } -- 2.38.1