From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f177.google.com (mail-dy1-f177.google.com [74.125.82.177]) (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 326B47260A for ; Mon, 19 Jan 2026 20:46:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768855606; cv=none; b=smaYK1Yw72Az5WKVR083RhTjipYCj0rFVUAm/IyLsvjItrJl80ec1CJtgPghlnnc+3EgG/LSpxvTflykyqCJ3VdfXlhLUnsBWE1HynWf/jPH1QrhLOy5e9S+9ES7NNjcWHyb5+OFVloAXOYBfF32YWGLn1bEYmKVuMCx5LWQK+4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768855606; c=relaxed/simple; bh=GThpleLyVlAzIlq7NuE8Ybc0GuZ4EhZQkax0YhHOBP4=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=eV+pXEEd2rTawcT3wY8uk5VSMjTPZpHQjJOmHzkZQwSSpZGnp48zw0C48wD10csfoRls3vLewWcYhQQvGmVAtIWRsgaDmFlephRXE9t+z4OQRFcwhKKQygDLiKX9NzfPa9G7DwwsNw6u9+GQFfHvAnQMsLkUzkAQdF5OKI6GqLs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=asu.edu; spf=pass smtp.mailfrom=asu.edu; dkim=pass (2048-bit key) header.d=asu.edu header.i=@asu.edu header.b=VCU5/KOT; arc=none smtp.client-ip=74.125.82.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=asu.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=asu.edu Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=asu.edu header.i=@asu.edu header.b="VCU5/KOT" Received: by mail-dy1-f177.google.com with SMTP id 5a478bee46e88-2b6c6f89f23so5247055eec.1 for ; Mon, 19 Jan 2026 12:46:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=asu.edu; s=google; t=1768855604; x=1769460404; darn=vger.kernel.org; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :from:to:cc:subject:date:message-id:reply-to; bh=GThpleLyVlAzIlq7NuE8Ybc0GuZ4EhZQkax0YhHOBP4=; b=VCU5/KOTLtwnzkNNi24bWWknbQiIG/v3iEMWWTpPeOBf6TZDdE3MJ/YSpYfEVNVtYI 2OR1gxWqpjfW9Vm/foo3mJkIFBH3xKNTo5wfbF7O0YjFpFzZLO3IUPTyofuzCxtVn+EK WCjb9IR3k3kAXmrgtBd2t0tItaFwxv9DCXZB1jHKY0yy8goSVSC4o0ITCgbP1HU9XdQR Ab7CtDh+0DvEcneczqnmRlCDH6X9hP+UlLQ8T18Ti7Ag5vi1MT9y03qvPyxiN5wW9kWJ UWta2dPYOArUXAbUUxTFtutI/Vmr6+9Lx/9vIPHzeRaKc8tN+xVWyBvYQKFj0FRcRASd UK4Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768855604; x=1769460404; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=GThpleLyVlAzIlq7NuE8Ybc0GuZ4EhZQkax0YhHOBP4=; b=juueZBJu0JTCA3oBnQ+a7SKwX3+FP18TxzZMvNVphOKMOuhEf0+vzfFEda4u7+rOJJ F19kOhiI9EAIQyHoMlXnMm+x9ehhHxgqZa44JEUSewop1iIHL3D2dn91D4Sm8yxN+PLK x+p3/VH18SWr0QdCjw70VcORDvSMNd2VIDD63N4bEUNqBkXHu6EJhiDnq5eNQDTHYF8+ W673y+y9YdtlsLQYD/k4hGUKO4dIQahy3VUqYgReuxdu9tGjd6ogbZh1/BKH5yE2YlIE OIa4wNVchi5361Cm4YzQIbNNXy+purfOBkHoepgidfcJWTMfxjWCnH4+xRTdJsF+9zfz R0xg== X-Forwarded-Encrypted: i=1; AJvYcCWFpQDwHfTGj4bXZ5ZB19Ceq3RYeT4QGtyB/RfAGSSc/53UtQWcu8Wtxbn6IaCJG1imz/xdtIO1vuMirYASAX8egoq+jyU=@vger.kernel.org X-Gm-Message-State: AOJu0Yy01VIcAT4LCgBiZBb17tcwNKA/jI8Fh2VqhrFcTM2HM63NFiZ5 6oa8im7RHkl7ABSlPlY5QfD8ax85Q2nSuFNN3ASTbM19Dvug7Id+3xwmppdNYAMAPA== X-Gm-Gg: AZuq6aJwD0yrZwOYNTnMlvj3x5ZSZLaiRLgywJPGCr0Koq/HvqZn4Zb5bInllmcHD5S jvslfPCytQWlNNXANuW+XfPsnrfkNMl8i1g/enkAKC0zJyW/6NAtxcYrh+oFYHw7DCNL0mFeWW5 tkiK6tJ1kH8VxGVnBjZLLBkz/4dcKAvrwZ1gg+iyDtVHuSYv78g67RB8WrvDObMV9/iKTTQfr7w SYBv9Q9xCQTOfQphaabBs+jeD9vbqNPpFtVIw7b8eTkhkPNNiUz0ZTAcoMO4yvrUI52f52KWfpp kAXZzHkXi+GUzmkxwNoU7cu5hAGu3L1zF/aM/mCeLocTHWlxkWDzWwEjUscMKxcYrQ454DFDzcI RNp2VLcPqMHkqcIcJHMWhJaJdljsUy0Iqj5IErwuhraMrWgcWLq71tdt3p4ECAmhakLCtrDP1F7 fUZOeVe13PoUsDLwtuZAIk0DMV9OizxvPfM2Tm8d6OKmc= X-Received: by 2002:a05:7301:4196:b0:2b4:7c92:3f81 with SMTP id 5a478bee46e88-2b6b381df3emr8278030eec.0.1768855602827; Mon, 19 Jan 2026 12:46:42 -0800 (PST) Received: from gmail.com (209-147-139-190.nat.asu.edu. [209.147.139.190]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b6b351e38bsm14264767eec.14.2026.01.19.12.46.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Jan 2026 12:46:42 -0800 (PST) Date: Mon, 19 Jan 2026 13:46:40 -0700 From: Will Rosenberg To: whrosenb@asu.edu Cc: Paul Moore , "David S. Miller" , David Ahern , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Huw Davies , netdev@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: ipv4: cipso potential BUG() Message-ID: Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Previously, it was discussed that skb_cow() has a bug due to implicit integer casting that can lead to a BUG when headroom < -NET_SKB_PAD. We concluded that it was not worthwhile to fix the root cause and to instead fix the symptom found in calipso. The thread for this issue can be found here: https://lore.kernel.org/netdev/CAHC9VhQmR8A2vz0W-VrrhYNQ2wgCYxHbAmdgmM2yTL-uh4qiOg@mail.gmail.com/ I recently reviewed the use cases of skb_cow() throughout the kernel and found that cipso_v4_skbuff_setattr() comes very close to triggering the same BUG. However, I concluded this was not triggerable. Even though len_delta can become negative, leading to a negative headroom passed to skb_cow(), we do not satisfy the condition headroom < -NET_SKB_PAD. Nonetheless, I believe cipso is using skb_cow() dangerously, but since the issue is not triggerable, would it still make sense to patch it? I figured I would throw out a quick email. Please let me know and I can make a similar patch for cipso if necessary. -- Will Rosenberg