From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay8-d.mail.gandi.net (relay8-d.mail.gandi.net [217.70.183.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E80251AE01D; Tue, 10 Dec 2024 14:58:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733842736; cv=none; b=Hgatr1FpQcr2sxLUB/L8RxX+2taKbJc68vfEKKcCxicRUhWPyToZqDweuhCmlfKywUUjYbacEqvL0RytzN9pe74GYpQNiZiqfeanfoKSG9zuyFMWKTmg3y83k9v4r6TVphcC1J8aFTH9kCQa7xa4AbBwhpCms4cAqNKHrKUoZy4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733842736; c=relaxed/simple; bh=hDw7FBC5IO4sAeB4JTfWIbLu6rTXTcS6KrWiZLaOcO8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lZjj2ftFXWfdM7VM0ht464oBkKyqU4+WPxht70pttdWp2NeA+Y+wAxwj6gRqUHqKfUX8CtYDEMD8AFgR5Bg4etoD2Qj4sLHuYnOyqDhS0J6KCu/2uuVU/X/2vKR7HbEKZzs6EYNcHUked7BLGcpUJdXY04mg5FnwKlqLAzYCGpE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=clip-os.org; spf=pass smtp.mailfrom=clip-os.org; dkim=pass (2048-bit key) header.d=clip-os.org header.i=@clip-os.org header.b=oXlDs6r1; arc=none smtp.client-ip=217.70.183.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=clip-os.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=clip-os.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=clip-os.org header.i=@clip-os.org header.b="oXlDs6r1" Received: by mail.gandi.net (Postfix) with ESMTPSA id D22FA1BF206; Tue, 10 Dec 2024 14:58:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=clip-os.org; s=gm1; t=1733842725; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=f/gb/aFXJz3nmCeqMOwXgNVxlqxmAWHfvgPVB0L32PQ=; b=oXlDs6r1u0Ik33AJQzEDQS8HctZuNfqL2EW7HaplSAanWrSoUlm2vJL0rG1GPEsZjvkZCb SCvXMH9F7NOcY65xqHSNUv5X5TpTowlXInFl76BD8EFbBzzZh6dlRt5ELzMwsBpo8jXkAb BAgUa7/EyZp3QbM+RIhSVaXjj7yq4W0wMrpMnUT8RYJTx0B3pJBvcCQ5QCih/KU0FwgUHo 0N3HzJV3LqX27vroTEos3DSOUj8GPKEod3Yqdq6ZnFrOxA8ySDSrG8744DaQttf5/tKl9i qazR7H4W9WEkq+nWq5ngdsQPlb/HqMIxh9LPUUrk0PCLUasfGbB1lm51SC9ymQ== Message-ID: <2d5447b7-c185-4ce9-852e-b56a28b0306a@clip-os.org> Date: Tue, 10 Dec 2024 15:58:41 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] sysctl: Fix underflow value setting risk in vm_table To: Joel Granados Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-fsdevel@vger.kernel.org, Nicolas Bouchinet , Greg Kroah-Hartman , Jiri Slaby , Alexander Viro , Christian Brauner , Jan Kara , Luis Chamberlain , Kees Cook , Joel Granados , Andrew Morton , Neil Horman , Lin Feng , Theodore Ts'o References: <20241114162638.57392-1-nicolas.bouchinet@clip-os.org> <20241114162638.57392-3-nicolas.bouchinet@clip-os.org> <4ietaibtqwl4xfqluvy6ua6cr3nkymmyzzmoo3a62lf65wtltq@s6imawclrht6> Content-Language: en-US From: Nicolas Bouchinet In-Reply-To: <4ietaibtqwl4xfqluvy6ua6cr3nkymmyzzmoo3a62lf65wtltq@s6imawclrht6> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-GND-Sasl: nicolas.bouchinet@clip-os.org Hi Joel, Thank's for your reply. I apologize for the reply delay, I wasn't available late weeks. On 11/20/24 1:53 PM, Joel Granados wrote: > On Thu, Nov 14, 2024 at 05:25:51PM +0100, nicolas.bouchinet@clip-os.org wrote: >> From: Nicolas Bouchinet >> >> Commit 3b3376f222e3 ("sysctl.c: fix underflow value setting risk in >> vm_table") fixes underflow value setting risk in vm_table but misses >> vdso_enabled sysctl. >> >> vdso_enabled sysctl is initialized with .extra1 value as SYSCTL_ZERO to >> avoid negative value writes but the proc_handler is proc_dointvec and not >> proc_dointvec_minmax and thus do not uses .extra1 and .extra2. >> >> The following command thus works : >> >> `# echo -1 > /proc/sys/vm/vdso_enabled` > It would be interesting to know what happens when you do a > # echo (INT_MAX + 1) > /proc/sys/vm/vdso_enabled Great question, I'll check that. > > This is the reasons why I'm interested in such a test: > > 1. Both proc_dointvec and proc_dointvec_minmax (calls proc_dointvec) have a > overflow check where they will return -EINVAL if what is given by the user is > greater than (unsiged long)INT_MAX; this will evaluate can evaluate to true > or false depending on the architecture where we are running. Indeed, I'll run tests to avouch behaviors of proc handlers bound checks with different architectures. > > 2. I noticed that vdso_enabled is an unsigned long. And so the expectation is > that the range is 0 to ULONG_MAX, which in some cases (depending on the arch) > would not be the case. Yep, it is. As I've tried to explain in the cover letter (https://lore.kernel.org/all/20241112131357.49582-1-nicolas.bouchinet@clip-os.org/), there are numerous places where sysctl data type differs from the proc handler return type. AFAIK, for proc_dointvec there is more than 10 different sysctl where it happens. The three I've patched represents three common mistakes using proc_handlers. > > So my question is: What is the expected range for this value? Because you might > not be getting the whole range in the cases where int is 32 bit and long is 64 > bit. > >> This patch properly sets the proc_handler to proc_dointvec_minmax. >> >> Fixes: 3b3376f222e3 ("sysctl.c: fix underflow value setting risk in vm_table") >> Signed-off-by: Nicolas Bouchinet >> --- >> kernel/sysctl.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/sysctl.c b/kernel/sysctl.c >> index 79e6cb1d5c48f..37b1c1a760985 100644 >> --- a/kernel/sysctl.c >> +++ b/kernel/sysctl.c >> @@ -2194,7 +2194,7 @@ static struct ctl_table vm_table[] = { >> .maxlen = sizeof(vdso_enabled), >> #endif >> .mode = 0644, >> - .proc_handler = proc_dointvec, >> + .proc_handler = proc_dointvec_minmax, >> .extra1 = SYSCTL_ZERO, > Any reason why extra2 is not defined. I know that it was not defined before, but > this does not mean that it will not have an upper limit. The way that I read the > situation is that this will be bounded by the overflow check done in > proc_dointvec and will have an upper limit of INT_MAX. Yes, it is bounded by the overflow checks done in proc_dointvec, I've not changed the current sysctl behavior but we should bound it between 0 and 1 since it seems vdso compat is not supported anymore since Commit b0b49f2673f011cad ("x86, vdso: Remove compat vdso support"). This is the behavior of vdso32_enabled exposed under the abi sysctl node. > > Please correct me if I have read the situation incorrectly. You perfectly understood the problematic of it, thanks a lot for your review. I'll reply to above questions after I've run more tests. I saw GKH already merged the third commit of this patchset and backported it to stable branches. Should I evict it from future version of this patchset ? Thanks, Nicolas > > Best >