From nobody Fri Dec 19 12:06:58 2025 Received: from mail-pl1-f178.google.com (mail-pl1-f178.google.com [209.85.214.178]) (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 9893C13A25B for ; Tue, 27 Aug 2024 08:12:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724746334; cv=none; b=k2/5WTRiIBGljSRJ063bbaur6ALs4srJCmmwp2RmI7kS0/YU/KRL5h0tBRZuE4f25Th6Dfmx+sXE/YAPJcfOv91UaihwKD5FFCQZrx+k9/tsFYKSqbUq/hoBEdHDEfxTU9cNLe9RfK9wlim7jZ2TR17U18SIXvtk8/eIfxxLRJU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724746334; c=relaxed/simple; bh=1zhjPy35tAft0ML3E1rzPPQg/5mwiHuG7IzmJoqGCfc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=CMBl5j66eRH6CDz86yp7xARVINn4ke+c/SaIE9AKdrVufLZQRMcPfSY7bbGrijONemyplYSr+4HoKjj8Yhxw01rBdpupkVxr5fKz35m6TC//UqkVFkoxPavK+b59tYYs0bUiTCn7SAcgDc+0pUc0cSVzTwSHMXIXneblarU9bYE= 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=UK0kRw2I; arc=none smtp.client-ip=209.85.214.178 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="UK0kRw2I" Received: by mail-pl1-f178.google.com with SMTP id d9443c01a7336-201e2fe323aso2713615ad.2 for ; Tue, 27 Aug 2024 01:12:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1724746332; x=1725351132; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=6eyASXvFFBLrRxfnlPxEMs4Lhi6ZcRK67/88H1vNg4I=; b=UK0kRw2Ie6aqlnDx78FckML2r4A6eS8AA1XMbgm+l8fmo5/T7wS3PerMh07b1rrnzi GdHdil0wQXyfXIi8ZeyqcSH/OnLSaM1XSu9sOWa+uBXvPPAzQLIIi3F80LYQ13nKsweK fZB0FoRhEBF2XyM7UQdafZwXabT8jEtrFYoAIlVDc3P7pLg53LzFK9Bydur9NtDyT3a1 GMMBvovOLXef7sxMDhyWtQO+lWQhuJp0hPTs8saDebIzTrjcItiGUGfUUJrR++E+jAyk NOMZN5o+t48yAmLt0yHyxZd2Iw0A0MZiBrHw8QdydPnkh6Uu8lK3tFh4TZvROish8MHK 1hrQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1724746332; x=1725351132; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=6eyASXvFFBLrRxfnlPxEMs4Lhi6ZcRK67/88H1vNg4I=; b=uKHYuUOePwkD1DBuoSNKV+KpXohlX1qMO9BEZ80mbSPEA2ZoTMU9RAVOmitsfZu0pn P+6nzEKWSn/PgT23TkbIg1K6jgwqaOekudeX5ug+l8WtuQ3S+imQX66APcx5riNHu9hR dJg2lgclMslCt5XNPLWyDVFrvCiDHFvELuKMF4m8ZkI9D3Ri1xzje879wmXadbqFjPfP WvhVbZ+KnJwtNn5IhLvjvRoYddK71AAxCr7877CH7xV8Miihi3fu2RYzDBVS8RUj222+ k18gEScrFyy4TzuwHcNpTeiVa9t5N3xMjonP+HFvG+HqlzPRJHb9fnT+aKtWswNKkYUk TFZA== X-Gm-Message-State: AOJu0YwwIf7TKaO5dYb9Ys7cxzn8AHnc7COJU8hZqdGc3ynyg9Bltkmt WRcNIRcXhCGx49fD1Yw/VO+Fyg8Oo+JCKneLgINooATEnulEUwAo X-Google-Smtp-Source: AGHT+IE9Lx4C7FqZirHSDtcCNwvnG8C6KW6FoCsLKETWZ4N2KdxiCpdD8C00jV89+kJ7dDlKQd8SDg== X-Received: by 2002:a05:6a20:918b:b0:1c4:d11d:4916 with SMTP id adf61e73a8af0-1cc8a07737cmr10040372637.7.1724746331658; Tue, 27 Aug 2024 01:12:11 -0700 (PDT) Received: from localhost.localdomain ([49.0.197.176]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-714342e4417sm8313732b3a.97.2024.08.27.01.12.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Aug 2024 01:12:11 -0700 (PDT) From: sunyiqi To: gregkh@linuxfoundation.org, rafael@kernel.org Cc: linux-kernel@vger.kernel.org, sunyiqi Subject: [PATCH] cpu: add CAP_SYSLOG check for reading crash_notes address Date: Tue, 27 Aug 2024 16:11:33 +0800 Message-Id: <20240827081133.872741-1-sunyiqixm@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" CPU crash_notes value can be obtained through /sys/devices/system/cpu/\ cpu[NUM]/crash_notes for leaking the phys address(introduced in kernel 5.10-rc1, but some distributions may migrate this feature to 4.x kernel). The relevant function is crash_notes_show() in file drivers/base/cpu.c. Though crash_notes file permission is 400 and owner is root:root, but in container, the root user can also read crash_notes which leads to information leak as most of kernel pointer value can not by read for root user in container without CAP_SYSLOG capability. In current linux kernel implementation, kernel pointer value or address printked by %pK is not directly exposed to root user in container. For kernel interface which includes those values, like /sys/kallsyms, /proc/net/packet, etc., address values are guarded by kernel function restricted_pointer(). Without CAP_SYSLOG capability, value 0 or NULL will be returned for reading those interfaces in container using root user. In restricted_pointer() and container, address values only returned by kernel when root user has CAP_SYSLOG capability which is not the default capabilities for Docker container. CAP_SYSLOG prevents root user in container to get kernel pointer from lots of interfaces based on printk, but not for cpu crash_notes. Add CAP_SYSLOG permission check in crash_notes_show() for viewing kernel address. Fixes: aa838896d87a ("drivers core: Use sysfs_emit and sysfs_emit_at for sh= ow(device *...) functions") Signed-off-by: sunyiqi --- drivers/base/cpu.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index fdaa24bb641a..a2f27bb0ffe6 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -156,6 +156,9 @@ static ssize_t crash_notes_show(struct device *dev, unsigned long long addr; int cpunum; =20 + if (!has_capability_noaudit(current, CAP_SYSLOG)) + return sysfs_emit(buf, "%llx\n", 0ull); + cpunum =3D cpu->dev.id; =20 /* --=20 2.34.1