From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id CAB7C3608A for ; Fri, 5 Jan 2024 20:20:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="NylGFNP1" Received: from [192.168.86.69] (unknown [50.46.228.62]) by linux.microsoft.com (Postfix) with ESMTPSA id 3002920ACF28; Fri, 5 Jan 2024 12:20:32 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 3002920ACF28 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1704486032; bh=Jng59x8KZZzeeKQplCW4Mnyyjjv+JKhOVrV66k6VW20=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=NylGFNP1gdVXY97xo9R3nBgGfCVDcGECUYt/azKYbEkf7ePEKLvaPlks7Hc4YdjxT w0ATGMkoBy9Iap8+TEPoaZShTqzAHtrZn8y0LSf1fO3uO7JnzhtNnA1c4km55YFUc/ e1NCtdxDwm+h5T64l3nvvz5K2CYNKHQWVcJvl/5A= Message-ID: Date: Fri, 5 Jan 2024 12:20:31 -0800 Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 6/7] ima: configure memory to log events between kexec load and execute Content-Language: en-US To: Mimi Zohar , roberto.sassu@huaweicloud.com, roberto.sassu@huawei.com, eric.snowberg@oracle.com, stefanb@linux.ibm.com, ebiederm@xmission.com, noodles@fb.com, bauermann@kolabnow.com, linux-integrity@vger.kernel.org, kexec@lists.infradead.org Cc: code@tyhicks.com, nramas@linux.microsoft.com, paul@paul-moore.com References: <20231216010729.2904751-1-tusharsu@linux.microsoft.com> <20231216010729.2904751-7-tusharsu@linux.microsoft.com> From: Tushar Sugandhi In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/20/23 12:15, Mimi Zohar wrote: > Hi Tushar, > > The Subject line should include the word "extra". The use of the > extra memory isn't limited to the measurements between the kexec load > and exec. Additional records could be added as a result of the kexec > load itself. Let's simplify the title to "ima: make the kexec extra > memory configurable". > > Please remove any references to measurements between kexec load and > execute. > Thanks Mimi. I will make these changes. > On Fri, 2023-12-15 at 17:07 -0800, Tushar Sugandhi wrote: >> IMA currently allocates half a PAGE_SIZE for the extra events that would >> be measured between kexec 'load' and 'execute'. Depending on the IMA >> policy and the system state, that memory may not be sufficient to hold >> the extra IMA events measured after kexec 'load'. The memory >> requirements vary from system to system and they should be configurable. > > The extra memory allocated for carrying the IMA measurement list across > kexec is hardcoded as a half a PAGE. Make it configurable. > Will do. >> Define a Kconfig option, IMA_KEXEC_EXTRA_MEMORY_KB, to configure the >> extra memory (in kb) to be allocated for IMA measurements added in the >> window from kexec 'load' to kexec 'execute'. > >> Update ima_add_kexec_buffer() function to allocate memory based on the >> Kconfig option value, rather than the currently hardcoded one. >> >> Signed-off-by: Tushar Sugandhi >> --- >> security/integrity/ima/Kconfig | 9 +++++++++ >> security/integrity/ima/ima_kexec.c | 13 ++++++++----- >> 2 files changed, 17 insertions(+), 5 deletions(-) >> >> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig >> index 60a511c6b583..8792b7aab768 100644 >> --- a/security/integrity/ima/Kconfig >> +++ b/security/integrity/ima/Kconfig >> @@ -338,3 +338,12 @@ config IMA_DISABLE_HTABLE >> default n >> help >> This option disables htable to allow measurement of duplicate records. >> + >> +config IMA_KEXEC_EXTRA_MEMORY_KB >> + int >> + depends on IMA && IMA_KEXEC >> + default 64 > > Since this isn't optional, the default should remain as a half page. > Since a page is architecture specific, the default will need to be arch > specific. > > thanks, > > Mimih > It was a feedback from Stefan in the V2 of this series to convert it from number of PAGES to KB.[1] But I can revert it to number of pages again. Also, making the default value as a fraction (1/2 page) feels weird for a CONFIG variable. Is it ok to make the default value as one page rather than half page? [1] https://lore.kernel.org/all/15a12e79-2e90-28f7-ffa3-ff470c673099@linux.ibm.com/ >>> +config IMA_KEXEC_EXTRA_PAGES >>> + int >>> + depends on IMA && IMA_KEXEC >>> + default 16 >>> + help >>> + IMA_KEXEC_EXTRA_PAGES determines the number of extra >>> + pages to be allocated for IMA measurements added in the >>> + window from kexec 'load' to kexec 'execute'. >> >> >> On ppc64 a page is 64kb. I would ask for additional kb here. >> >> > Not sure I understand. Do you mean I should make the default value of > the config IMA_KEXEC_EXTRA_PAGES 64 or something? No, what I mean is you should ask the user for how many extra kilobytes (kb) to allocate - not ask for pages. Stefan >> + help >> + IMA_KEXEC_EXTRA_MEMORY_KB determines the extra memory to be >> + allocated (in kb) for IMA measurements added in the window >> + from kexec 'load' to kexec 'execute'. >> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c >> index 55bd5362262e..063da9c834a0 100644 >> --- a/security/integrity/ima/ima_kexec.c >> +++ b/security/integrity/ima/ima_kexec.c >> @@ -128,15 +128,18 @@ void ima_add_kexec_buffer(struct kimage *image) >> int ret; >> >> /* >> - * Reserve an extra half page of memory for additional measurements >> - * added during the kexec load. >> + * Reserve extra memory for measurements added in the window from >> + * kexec 'load' to kexec 'execute'. >> */ >> - binary_runtime_size = ima_get_binary_runtime_size(); >> + binary_runtime_size = ima_get_binary_runtime_size() + >> + sizeof(struct ima_kexec_hdr) + >> + (CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB * 1024); >> + >> if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE) >> kexec_segment_size = ULONG_MAX; >> else >> - kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + >> - PAGE_SIZE / 2, PAGE_SIZE); >> + kexec_segment_size = ALIGN(binary_runtime_size, PAGE_SIZE); >> + >> if ((kexec_segment_size == ULONG_MAX) || >> ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) { >> pr_err("Binary measurement list too large.\n"); >