From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f41.google.com (mail-wm1-f41.google.com [209.85.128.41]) (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 C0CA929D281 for ; Thu, 21 May 2026 16:46:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779381999; cv=none; b=FxzqZwuTTPtYMQbWNKtsAAWnBjKZ4DPKDzpJaxGoPdLPiWEwMQnplGvQgtp7ggZPVsSV+phkp3cImlryrUFQBER+F5h15HzHr+BJW4joLB9PZAclmN5Goon6DOxFT/Coh76knrLepta6cqHahZwHLCDZ52EG8t2aRmFaTPkPOFU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779381999; c=relaxed/simple; bh=55HpdrZ1XWqM3uwC+a47+vakAvshOA/Toys7NpGVJzc=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Num88/U3hTEavpzEraO4amto78Q9+7OgCwDNon4YQS3dP0dAYGbwYmHapJlq6YxUdkUhrFZEczzgLT00TOiR67zaLApKFFnPDaIdRZNZW19q2IIQPnjvRjnvci2I7FUKtH74P+QBOxJHpKp1DYoHHdBd1w8LhVyxrgJTwGcjIVY= 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=hAiFXflX; arc=none smtp.client-ip=209.85.128.41 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="hAiFXflX" Received: by mail-wm1-f41.google.com with SMTP id 5b1f17b1804b1-490388fd0dbso8750335e9.0 for ; Thu, 21 May 2026 09:46:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1779381995; x=1779986795; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=NA/nM16UoxaTsk3A7SWQL7q3HkgK647mNtY2rDcRyyc=; b=hAiFXflXTEbRl6U5Air/vBGryJ1P7DUwv5y5hFcBfrvyOOjvwLAPWk6boHEMfrP+03 djrSF/MmhRRc4oKAARffcHojm9lrMfH/yxDwEmaCsT4BFCL3flmfjoZXGq6TFSC3TeHl JsiTufiR6et1mz+pI8XV2U+9x+ymMfxMCAW0bX+y+95+67AVxLZvt8B0iLXkU9d/aiqe 9TLZTYgekPiyf54s88p+J1C3j1Lc4MyofWrYIv5jQC1MQsWTxKDTJulTH9sW3bkKM6Er 8ENfEnS8Rye+RBlr7U5dk7H7qISkWK2Sz6IRcVfJFcdljcS2gaAHhL/dDTECxI2slWnI yang== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779381995; x=1779986795; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=NA/nM16UoxaTsk3A7SWQL7q3HkgK647mNtY2rDcRyyc=; b=EqK0jnZd34QewSRFiD4cz7TsBpCMgFiaM0YkgIVpH4XDIz5CYzxqaFieGd9unynwWB Ts4FsJOKrLCk6UXF6M7gqQ29DqIKgBJ4vmBm9iYvY8lve6twNCw9Q/bbFcZULhTCmooX SxbceS8x1Oe0JBB7aMzbchv198Ujf7rB0/IOymFZyT+apGuu27NbC0NZUm3gnUS19wU0 u+6H5DHOJ8249AG0LhaN/7kU2lITI4Flmt2KhL7szlp/SpWKb2+XseTpkPdnXK2bze2E ujTyVVpjrY5KqDYYeZDywVUEL/lPiTsnL+i81qoZLkmK+lfRjNOwQqn2QrmBu3wt4+Rd /R8w== X-Forwarded-Encrypted: i=1; AFNElJ/p7i0unCEK1cPlP8t67XROD5NQyecLjO7XW8lEX0Yzlqo2RRHplEWuc51esFH9kOmNV3/Azfzoe7Bo@vger.kernel.org X-Gm-Message-State: AOJu0YxAWiUa2gOnISie5gmgHv9TzmRmZ6R8+mn6YIwybLGG5MgxNJU0 un57C+Nx2sdOxdTB3va0AJ6axIf4uei5AlT5mxQL18bydteKdRxMRy9a X-Gm-Gg: Acq92OGJ7UiRSmRjZGS/hFPKtzK4RwK1EhkdH6wAQvL8QehimDAoUmi5DlhCjwK5Wte sY37ZKxiY8QGm45X5nHZFmABh2nJhv+Qzm/ShOYNfFNf8XhFnscxN5Lfj6/H4j9op2YnJjPaldW L+bMHbpK594bJXFIigjeueCUUKvYnpUMQQyVVkMRNAKtdxhSbKpFEFuhtNzjz39H6h9XEZdp5IB tS8f3kkwYylpB03ICuOoJQeIJxvjXIym/rMzaN0fsrDsH4kUKONHCxus+93GWpkgB3TQxzf2Hvr 8PndniFivh3K0cyaOcGcvUGCNLXpWgtK7xgG4f2XDha8zpZtXT2NqDrn9k3TBPmL8g1ps4ey+y4 gAHN/dfEkgRgz512MlEgOusBDImEaoH6WpXotr3Xv8hVmwMFx4HTgFvmbj62hyiR7W8jHj/8BT4 T+/isM14bxTHkHdOBUkoGTtsRONOw7U2L2SLkN7bq5zho5bdD8ATwlJuQewoFWBltO X-Received: by 2002:a05:600c:45c6:b0:488:ac01:72de with SMTP id 5b1f17b1804b1-49036033502mr53623425e9.5.1779381994891; Thu, 21 May 2026 09:46:34 -0700 (PDT) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49035ecac15sm31613075e9.6.2026.05.21.09.46.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 May 2026 09:46:34 -0700 (PDT) Date: Thu, 21 May 2026 17:46:31 +0100 From: David Laight To: Kees Cook Cc: Luis Chamberlain , Pengpeng Hou , stable@vger.kernel.org, Petr Pavlu , Richard Weinberger , Anton Ivanov , Johannes Berg , "Rafael J. Wysocki" , Len Brown , Corey Minyard , Gabriel Somlo , "Michael S. Tsirkin" , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Bart Van Assche , Jason Gunthorpe , Leon Romanovsky , Laurent Pinchart , Hans de Goede , Mauro Carvalho Chehab , Bjorn Helgaas , Hannes Reinecke , "James E.J. Bottomley" , "Martin K. Petersen" , Daniel Lezcano , Zhang Rui , Lukasz Luba , Greg Kroah-Hartman , Jiri Slaby , Alan Stern , Jason Wang , Xuan Zhuo , Eugenio =?UTF-8?B?UMOpcmV6?= , Jason Baron , Jim Cromie , Tiwei Bie , Benjamin Berg , Ilpo =?UTF-8?B?SsOkcnZpbmVu?= , "David E. Box" , "Maciej W. Rozycki" , Srinivas Pandruvada , Peter Zijlstra , Heiko Carstens , Vasily Gorbik , Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Vinod Koul , Frank Li , Daniel Gomez , Sami Tolvanen , Aaron Tomlin , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrew Morton , John Johansen , Paul Moore , James Morris , "Serge E. Hallyn" , Andy Shevchenko , Georgia Garcia , kvm@vger.kernel.org, dmaengine@vger.kernel.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, linux-um@lists.infradead.org, linux-acpi@vger.kernel.org, openipmi-developer@lists.sourceforge.net, qemu-devel@nongnu.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-pci@vger.kernel.org, linux-scsi@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 01/11] params: bound array element output to the caller's page buffer Message-ID: <20260521174631.71a06440@pumpkin> In-Reply-To: <20260521133326.2465264-1-kees@kernel.org> References: <20260521133315.work.845-kees@kernel.org> <20260521133326.2465264-1-kees@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 21 May 2026 06:33:14 -0700 Kees Cook wrote: > From: Pengpeng Hou > > param_array_get() appends each element's string representation into the > shared sysfs page buffer by passing buffer + off to the element getter. > > That works for getters that only write a small bounded string, but > param_get_charp() and similar helpers format against PAGE_SIZE from the > pointer they receive. Once off is non-zero, an element getter can > therefore write past the end of the original sysfs page buffer. > > Collect each element into a temporary PAGE_SIZE buffer first and then > copy only the remaining space into the caller's page buffer. Should this be using a 4k buffer on all architectures? Initially perhaps just using a different name for the constant until all the associated PAGE_SIZE limits have been removed. -- David > > Cc: stable@vger.kernel.org > Reviewed-by: Petr Pavlu > Signed-off-by: Pengpeng Hou > Signed-off-by: Kees Cook > --- > kernel/params.c | 26 ++++++++++++++++++++------ > 1 file changed, 20 insertions(+), 6 deletions(-) > > diff --git a/kernel/params.c b/kernel/params.c > index 74d620bc2521..752721922a15 100644 > --- a/kernel/params.c > +++ b/kernel/params.c > @@ -475,22 +475,36 @@ static int param_array_set(const char *val, const struct kernel_param *kp) > static int param_array_get(char *buffer, const struct kernel_param *kp) > { > int i, off, ret; > + char *elem_buf; > const struct kparam_array *arr = kp->arr; > struct kernel_param p = *kp; > > + elem_buf = kmalloc(PAGE_SIZE, GFP_KERNEL); > + if (!elem_buf) > + return -ENOMEM; > + > for (i = off = 0; i < (arr->num ? *arr->num : arr->max); i++) { > - /* Replace \n with comma */ > - if (i) > - buffer[off - 1] = ','; > p.arg = arr->elem + arr->elemsize * i; > check_kparam_locked(p.mod); > - ret = arr->ops->get(buffer + off, &p); > + ret = arr->ops->get(elem_buf, &p); > if (ret < 0) > - return ret; > + goto out; > + ret = min(ret, (int)(PAGE_SIZE - 1 - off)); > + if (!ret) > + break; > + /* Replace the previous element's trailing newline with a comma. */ > + if (i) > + buffer[off - 1] = ','; > + memcpy(buffer + off, elem_buf, ret); > off += ret; > + if (off == PAGE_SIZE - 1) > + break; > } > buffer[off] = '\0'; > - return off; > + ret = off; > +out: > + kfree(elem_buf); > + return ret; > } > > static void param_array_free(void *arg)