From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f170.google.com (mail-yw1-f170.google.com [209.85.128.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2940934A3BC for ; Fri, 27 Mar 2026 19:56:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774641411; cv=none; b=D4omX3vjijFYhvmvyzbJuouF1WGkLJNq/GJavPxn7rkQUuS2jLsDUIo+pMRx5VJlN966vVk4b2ci33q0vSQHU5refViTJx26ICr/OpNfffrVz+RIaYUnexBv937R2bzSWrLWClVDmO3k1+B68AvHqARdRrB52KQ3UidWaiDoSmY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774641411; c=relaxed/simple; bh=g2A1VodOn7M/F58Dvqm/kjBtZoSx4LJs+OGd3ZNIn1w=; h=Date:From:To:Cc:Message-ID:In-Reply-To:References:Subject: Mime-Version:Content-Type; b=IUzXaz9SxEC+GH40zFe2ymbGodt2m2FkFKbeSlXCfVJh6MJitiyolqNwkk4exP8MoGaBPoWiyDXBCz1LlR2Q5lvaek7HfPa0Hlp46OL49rUJYr66FrxRwqZ0SouU6HJ0s3GqzJhaoUQvtUbOT9ebVDqMYQ1mGgwLfsnDw+tXu78= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=lfMJmFwr; arc=none smtp.client-ip=209.85.128.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="lfMJmFwr" Received: by mail-yw1-f170.google.com with SMTP id 00721157ae682-7947cf097c1so26486047b3.2 for ; Fri, 27 Mar 2026 12:56:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1774641409; x=1775246209; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:subject:references :in-reply-to:message-id:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=li4dRdJMGvbSuyBJNoyrYjziCM6PRkPOEGU91wNCK34=; b=lfMJmFwr6P0oyTXAQxJBMlAk3b5tqm6tMeMHlDs5s+DeS51Mr/Of+x5/8M+3aQQiBy IAw7xQ/kLfJaSaNaL+fi7zxts0mCjLhTgSMNfGtLRdr2rehMXO4TPGdZ5pxNM5lcdNPP 83K1B3Wx2Cf99zzlAP00nCkDzdahX9K9LuNaNh2oYQVSCIiIV+Oxc5fsW619a4A7mIWc 0/Az3nWmBCwBeLdHw6Y4w2vVPtGnKTC4VY9uk8JkiSGoj9bRDA2RGcS3K2drV9xF2hPn J6y4A0NewtLd0rQn3I7PNTEH6tYGVGcVaS4NX3i3HM6An2kSLBinfRWhm/V0G6OOFMfy CZdQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774641409; x=1775246209; h=content-transfer-encoding:mime-version:subject:references :in-reply-to:message-id:cc:to:from:date:x-gm-gg:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=li4dRdJMGvbSuyBJNoyrYjziCM6PRkPOEGU91wNCK34=; b=Rii4zZ678I3fOYbdprWLIsQFILfsyhnCO2bTSYcZSvdN8QU9jAVqKzNyHzTJ6mYU+l CG6TjkOn+rkDViSZJ4u385Um//4o8a3w1cCoJcFHg+MqlVoMDjY6gVGMBkeRtiPPo5Nt b2PfudTRGrRl/+WL85CKfRbcMktDNmsoeQ4D5nJoc+bHrQz9eLwTomOzfrpYY4FfPTo3 Tf067X+It4nj5Zjv5+1WC2wq6v/Lqv6MEY/ub7xkh1OH+/I6lSJ65eLScz5yxditAj1W yoiUHM4aZGMVcJQAqL4X6GxSsC2wRuRl/GForWKCNvXk/tBMhRDzlvvpfZ+bOPMr9Nnr 9zVA== X-Forwarded-Encrypted: i=1; AJvYcCXv5Hr8VyqogTK07qLHD2cl19Q7bREgh/Sek6cO0NuEQcMzQ62snVw6ZbUtEuYQ7IuX3iJJly7yLWn3II0=@vger.kernel.org X-Gm-Message-State: AOJu0YwQ0XGPMW76PdxlZP/sPvz2FFS8CLmZdiLeu9ClMd2H36s2mVha N1O1NQrv+rlr/eSSwh2xF8Cs0RZgpUBoYiqSay1zUOZ06pDhL4tD5E+7 X-Gm-Gg: ATEYQzxGozL25mdJEMHOwV1HGScyui7biBk583KQFosFOPnq/cXgLnSFcvWSMXlFNMZ i6v5J6dOrvTfFXJy+BHEuo4YQ2eRXaj/00y2qah+5pZkVcWZI8fz4ot0apBXceW5YQnFiO4AOiI ZRWIk9ZfQYsjYPSyxfXLjhSZMI+N4Knma47bXxc0ECNveJiUYNWG2GJ9TVTCtb+zK9ytmI/FHN4 Il807gfEaDScH++qLJp6n9wkbzMcMJw0z3zFMdbkrmY5Q7SGNaxUkZGXX5SDS4QXZWDq16Oi/1q LeHQb4naE0FwFEcALTd9IClCG/DxCUDi9IGhqsEpQYjBorWNe5OVGubk7XutXjG73K6cEFxOZA1 gW011ACbGRua3tAPJvCio5HEkv4xCUBEAOz3aC+lNdI7SYgebtOCq7e3W5x6XoQLZpIuCn/0KEi 8nNc3wVuOvoaOcXk9PoIKB6SNxSs8JA8agOjc85nRsIdUHaNUhuiCMtj1TIdE6AxUI1rvOwE8df Ef9 X-Received: by 2002:a05:690c:e3e5:b0:79a:c396:bfb with SMTP id 00721157ae682-79bde0442f6mr36548767b3.43.1774641409099; Fri, 27 Mar 2026 12:56:49 -0700 (PDT) Received: from gmail.com (180.134.85.34.bc.googleusercontent.com. [34.85.134.180]) by smtp.gmail.com with ESMTPSA id 00721157ae682-79b1e3bec5dsm35125117b3.25.2026.03.27.12.56.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Mar 2026 12:56:48 -0700 (PDT) Date: Fri, 27 Mar 2026 15:56:47 -0400 From: Willem de Bruijn To: Guoyu Su , edumazet@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com Cc: willemdebruijn.kernel@gmail.com, netdev@vger.kernel.org, horms@kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com, Guoyu Su Message-ID: In-Reply-To: <20260327153507.39742-1-yss2813483011xxl@gmail.com> References: <20260327153507.39742-1-yss2813483011xxl@gmail.com> Subject: Re: [PATCH net v7] net: use skb_header_pointer() for TCPv4 GSO frag_off check Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Guoyu Su wrote: > Syzbot reported a KMSAN uninit-value warning in gso_features_check() > called from netif_skb_features() [1]. > > gso_features_check() reads iph->frag_off to decide whether to clear > mangleid_features. Accessing the IPv4 header via ip_hdr()/inner_ip_hdr() > can rely on skb header offsets that are not always safe for direct > dereference on packets injected from PF_PACKET paths. > > Use skb_header_pointer() for the TCPv4 frag_off check so the header read > is robust whether data is already linear or needs copying. > > [1] https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407 > > Link: https://lore.kernel.org/netdev/willemdebruijn.kernel.1a9f35039caab@gmail.com/ > Fixes: cbc53e08a793 ("GSO: Add GSO type for fixed IPv4 ID") > Reported-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407 > Tested-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com > Signed-off-by: Guoyu Su Reviewed-by: Willem de Bruijn Sashiko asks about similar inner_ip_hdr in skb_gso_has_extension_hdr, but userspace cannot set skb->encapsulation, so that's a false positive.