From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f176.google.com (mail-pl1-f176.google.com [209.85.214.176]) (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 0EB5C46D57C for ; Wed, 5 Aug 2026 12:57:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785934677; cv=none; b=VpTRXW8tdJO80rU1rMBVnJYSH27Id2AQQBNIxSKCXxywfkzCuqmwLmCojB/OitcayZWDKpBdel9kKxl4hvNlBAmOTlvvPWsu/WqtD6oTd5dPYgiznXgkjlEIvCgX66vwG8/AjWHdnjMAIw4rwOq/Y3Vyg6gYGho+pL6Humozxgo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785934677; c=relaxed/simple; bh=cKn0rvdC49BIcqAimFO1T40WDQRqjLgqEK6HkR4ZC2k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dW8hxVOP1/aeUMRp/i/HollDV33t9Agonnai8Xsjmd81ehfM62IXyQBp2ok0LJWOlxMi8AjuVU9Llc9I9+GwziESMFuzT4ILJf8zGD3quyTXW9bKiqBBjFHn1U2fuIyAW+kqobyX6TuX/pFzIjM7Bl9rRJSEnai24d3yyiTpmPw= 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=D8EjLPa1; arc=none smtp.client-ip=209.85.214.176 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="D8EjLPa1" Received: by mail-pl1-f176.google.com with SMTP id d9443c01a7336-2cecc8a3dbfso1193865ad.0 for ; Wed, 05 Aug 2026 05:57:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1785934675; x=1786539475; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=ALanzQpzebmmM5lW2CkhaK/fD5aNgZLXF16Jkbg/hKA=; b=D8EjLPa12Caudz5U0Zcjb/flPVecOlyL+K/E8WSu5csiD3YojXKRZw4285DgY8BLzX oz9ngnNfyAIvKzYcAXxq0r1f4HduhJiPlGFx0K1YzIpZCnh6mul0FnUZvoAOYq30BAH0 OqPOAvyADL5yg7tigZmgc2tAgfa85GyxYhfI1xrr3VWEiVG3qWN4VqRhTtn1cZbvZlEZ g0yOkoL3+9aqZxV3ORhA+Y2lrGesHEN72/ve7MGjElRpBVW6SephyB2ASPmxVQcL6OWu sw7Of3UeOSnFkgsTq6jtaQBZF1ehwZEgv5ROAdYvfJBWaww0/Oy7rnilKa6lHQqrMHbQ o20Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785934675; x=1786539475; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=ALanzQpzebmmM5lW2CkhaK/fD5aNgZLXF16Jkbg/hKA=; b=LOvUUXDyXzEQpq2QueEKXR2bfSNM6MDY/D/lbxzq0P+GhBSm5V0yhmdr/rm5oUeW2Q 7fnKEFE6m3nqDqviujwfLE3EltjKjjqU4fWgdDVQvvEApltS/O3eQl7ZR+BiBVQ7EObE TmDZ6zJveW4TVngs8GmCJa1wIF7DRXA5B3qv277WFSqXN8rgqPLxmksnHTrJAUBGVy59 /9WSek/V43hk3MWl8PsGbcnULnjSxjA0rR4HR5b55jFPGwREXtt+IJCbgCQe1UUJnS0p AvYcDmDMLIR6YNMK/TbilQwNnhOik94ylxKCqYtwfZsszfk44ydzUM3mQ2lWQozrQABq 2jdQ== X-Forwarded-Encrypted: i=1; AHgh+RrAUCKk43/XlbQFB4SkdOl+JbzzMTxzYDjVNYTlwH0im+yyoEKmRPNl2vQ85wpYx0eMN3Ur0Ik=@vger.kernel.org X-Gm-Message-State: AOJu0Yyrb54dknu8JlyZJlYfkQBn62h6akX5fyC2HLYzX+W+cx+1dF81 TQ78ZicBBYPzOqimeF6pilUOH3ws8vKK+MH3CUnYhIGBL6AGDNr6Y4N+ X-Gm-Gg: AR+sD13vM5T5ZnxK8CzdHLkCzVFXY+DFph/LiMdZtgLPWr8D3Po9/+TOm656FlwbLyO U4TWBbn3TViL6ArbJVwf77bMxawmrOejVf1KJIW7nhvsyD6Bm78Yq8vyC0H/6asvE6ZVKsnGpEp YfcaysxecmDxkl6Pfp0+gfmc7Pm+gZpYsORJDMnT2VnY9iI32CekrIothKt56tWkRk+/ODWEVHN WjGpQupjJBtf+2dMsNDHLjXBtZzgU7z+uzzXoSIHiVnnzOzEeyx1UjmaVP1Ao+5W6+hk7OWPeNp QNXY15fwKWGqKA1fX54klkHsnPQ35GQ/Gk4XYFCNPv56259kxNYvQ1WhQl5o+ZNjYUInr/s0u5h X72qSaW4GBtLwPa+Gll8W3pPtHGG7mLn2K6YqHLmV8r1KD1e/tcR/FiKxHJbq3HSn0apbQ5YTgW LU3nnp/V+7tTf6pn8VMo8dppbGpSCQ+Z4EkcOwyEXLs9MQaziaAOI4CDhvXYp3tcg1FODn1MOab ASNyb/d2K3qizY3eQAJIHoZsc0nkFv9nAJetf7M2Mzsjy94YGU= X-Received: by 2002:a17:903:468b:b0:2c7:ef84:c58e with SMTP id d9443c01a7336-2d0ca761dffmr56546565ad.1.1785934675269; Wed, 05 Aug 2026 05:57:55 -0700 (PDT) Received: from localhost.localdomain ([139.159.170.79]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d0a9f8fb4bsm16514625ad.5.2026.08.05.05.57.48 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 05 Aug 2026 05:57:55 -0700 (PDT) From: Qihang To: netdev@vger.kernel.org Cc: willemdebruijn.kernel@gmail.com, willemb@google.com, daniel.zahka@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, stable@vger.kernel.org, Qihang Tang Subject: [PATCH net v6 1/3] net: remove CAP_SYS_RAWIO zero-padding in dev_validate_header Date: Wed, 5 Aug 2026 20:57:27 +0800 Message-ID: <20260805125729.19220-2-q.h.hack.winter@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260805125729.19220-1-q.h.hack.winter@gmail.com> References: <20260805125729.19220-1-q.h.hack.winter@gmail.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Qihang Tang dev_validate_header() reads dev->hard_header_len directly when zero-padding short link layer headers for CAP_SYS_RAWIO holders: if (capable(CAP_SYS_RAWIO)) { memset(ll_header + len, 0, dev->hard_header_len - len); return true; } Packet send paths call dev_validate_header() on skbs whose headroom was allocated from an earlier hard_header_len read. If the device is reconfigured so that dev->hard_header_len increases before validation, the memset writes past the reserved buffer, an out-of-bounds write. This out-of-bounds write is masked in some SOCK_RAW paths today because the same concurrent increase can first make skb_push() exceed the reserved headroom and trigger skb_under_panic(). Remove the zero-padding branch before making those hard_header_len reads consistent, so the snapshot fixes do not turn a loud panic into a silent overwrite. This path is only reached for variable length L2 protocols, where len < hard_header_len but len >= min_header_len. No remaining in-tree variable length L2 protocol implements header_ops->validate, and the CAP_SYS_RAWIO bypass that zero-pads and accepts short headers has no real value beyond allowing testing of intentionally malformed input. Drop the CAP_SYS_RAWIO branch. The remaining reads of dev->hard_header_len in dev_validate_header() are comparisons only and have no memory safety impact. Suggested-by: Willem de Bruijn Fixes: 2793a23aacbd ("net: validate variable length ll headers") Cc: stable@vger.kernel.org Signed-off-by: Qihang Tang --- include/linux/netdevice.h | 5 ----- 1 file changed, 5 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 9981d637f8b5..9a770eb823ce 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3531,11 +3531,6 @@ static inline bool dev_validate_header(const struct net_device *dev, if (len < dev->min_header_len) return false; - if (capable(CAP_SYS_RAWIO)) { - memset(ll_header + len, 0, dev->hard_header_len - len); - return true; - } - if (dev->header_ops && dev->header_ops->validate) return dev->header_ops->validate(ll_header, len); -- 2.50.1 (Apple Git-155)