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 11C33221FAE; Tue, 29 Apr 2025 22:00:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745964025; cv=none; b=GsUKBfHdtPEAHqT+KK+zxyE8AnaM4K74NT/Tgzv7rZUG9Oh3LwRrVkvWYPAqhEnMeMB7MfzeNWtoVl/iSTnDfqXrsYFSiZg7O0GCs1kRu6frIyEi4yAwO5bl4cXlIBq1OLQitvYpPEkLssTbTNOBAJ1dsZZEfHmddDMr80S4iYg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745964025; c=relaxed/simple; bh=d3/Z6QPw0Cs9yNszPaQ5V2DD+FjaBrRTlSPNyNV0saA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TS6kkhyPRwH/aObFf+sBgB7foBMndIfJc3DBKHR5P7tdZucsj8CD149qZoZe40Bn8rEkrSzm/gm8Rl+m+wjCNgtm6cgzt/uyGNG/P96kRCZrmGBSKJaouVy2OVy4njKen9WRQwOIQ+ZwJgM7sjzNqp4fVducSxLQ0fSse3E6NsI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=svT14qQv; arc=none smtp.client-ip=13.77.154.182 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="svT14qQv" Received: from [100.70.192.100] (unknown [172.172.34.115]) by linux.microsoft.com (Postfix) with ESMTPSA id A055E21130A6; Tue, 29 Apr 2025 15:00:21 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com A055E21130A6 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1745964023; bh=GabYpzt6hKuuPORocEKZwZwL8u9mqEx7Hx0RkHPtTMs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=svT14qQvKRJ+l9WXAAjQjViQEabtZkIL7a6+9A2SiWIcaEE6oG3llA8Tle9Zg52/h mHL3oJsLKd+sYJYbDmLs/UAIfZO8ZSMyLetId+kOWFvupS0DrO0gferMEeKH4bCI7+ 4yLD9JSgsZHeObJHz6NRTySun/KqlZUUftz9U0cs= Message-ID: <2b352e35-5795-40da-bba6-c03347cfc5be@linux.microsoft.com> Date: Tue, 29 Apr 2025 15:00:20 -0700 Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 8/9] ima: make the kexec extra memory configurable To: Stefan Berger , zohar@linux.ibm.com, roberto.sassu@huaweicloud.com, roberto.sassu@huawei.com, eric.snowberg@oracle.com, ebiederm@xmission.com, paul@paul-moore.com, code@tyhicks.com, bauermann@kolabnow.com, linux-integrity@vger.kernel.org, kexec@lists.infradead.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Cc: madvenka@linux.microsoft.com, nramas@linux.microsoft.com, James.Bottomley@HansenPartnership.com, bhe@redhat.com, vgoyal@redhat.com, dyoung@redhat.com References: <20250421222516.9830-1-chenste@linux.microsoft.com> <20250421222516.9830-9-chenste@linux.microsoft.com> Content-Language: en-US From: steven chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 4/29/2025 12:06 PM, Stefan Berger wrote: > > > On 4/21/25 6:25 PM, steven chen wrote: >> From: Steven Chen >> >> The extra memory allocated for carrying the IMA measurement list across >> kexec is hard-coded as half a PAGE.  Make it configurable. >> >> Define a Kconfig option, IMA_KEXEC_EXTRA_MEMORY_KB, to configure the >> extra memory (in kb) to be allocated for IMA measurements added during >> kexec soft reboot.  Ensure the default value of the option is set such >> that extra half a page of memory for additional measurements is >> allocated >> for the additional measurements. >> >> Update ima_add_kexec_buffer() function to allocate memory based on the >> Kconfig option value, rather than the currently hard-coded one. >> >> Suggested-by: Stefan Berger >> Co-developed-by: Tushar Sugandhi >> Signed-off-by: Tushar Sugandhi >> Signed-off-by: Steven Chen >> Reviewed-by: Stefan Berger >> Reviewed-by: Mimi Zohar >> Acked-by: Baoquan He >> --- >>   security/integrity/ima/Kconfig     | 11 +++++++++++ >>   security/integrity/ima/ima_kexec.c | 16 +++++++++++----- >>   2 files changed, 22 insertions(+), 5 deletions(-) >> >> diff --git a/security/integrity/ima/Kconfig >> b/security/integrity/ima/Kconfig >> index 475c32615006..976e75f9b9ba 100644 >> --- a/security/integrity/ima/Kconfig >> +++ b/security/integrity/ima/Kconfig >> @@ -321,4 +321,15 @@ config IMA_DISABLE_HTABLE >>       help >>          This option disables htable to allow measurement of >> duplicate records. >>   +config IMA_KEXEC_EXTRA_MEMORY_KB >> +    int "Extra memory for IMA measurements added during kexec soft >> reboot" >> +    range 0 40 >> +    depends on IMA_KEXEC >> +    default 0 >> +    help >> +      IMA_KEXEC_EXTRA_MEMORY_KB determines the extra memory to be >> +      allocated (in kb) for IMA measurements added during kexec soft >> reboot. >> +      If set to the default value of 0, an extra half page of memory >> for those >> +      additional measurements will be allocated. > > If you have an IMA policy taking quite a few measurements and you are > fast after reboot to log in to initiate the 'kexec load' (While system > is still starting up), the system may end up with loss of measurements > very easily if the default is 0 and pages are small. -> Set the > default to the max? Also, would we expect distros to all go through > the new config option and choose 40 or will they likely leave it at 0? > Hi Stefan, Could you please check the comments of version V11 on this default value? https://lore.kernel.org/all/20250402124725.5601-1-chenste@linux.microsoft.com/ Thanks, Steven >> + >>   endif >> diff --git a/security/integrity/ima/ima_kexec.c >> b/security/integrity/ima/ima_kexec.c >> index ed867734ee70..d1c9d369ba08 100644 >> --- a/security/integrity/ima/ima_kexec.c >> +++ b/security/integrity/ima/ima_kexec.c >> @@ -118,6 +118,7 @@ void ima_add_kexec_buffer(struct kimage *image) >>                     .buf_min = 0, .buf_max = ULONG_MAX, >>                     .top_down = true }; >>       unsigned long binary_runtime_size; >> +    unsigned long extra_memory; >>         /* use more understandable variable names than defined in >> kbuf */ >>       size_t kexec_buffer_size = 0; >> @@ -125,15 +126,20 @@ 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 during kexec. >>        */ >> -    binary_runtime_size = ima_get_binary_runtime_size(); >> +    if (CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB <= 0) >> +        extra_memory = PAGE_SIZE / 2; >> +    else >> +        extra_memory = CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB * 1024; >> + >> +    binary_runtime_size = ima_get_binary_runtime_size() + extra_memory; >> + >>       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");