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 9206528150E; Thu, 10 Apr 2025 14:12:56 +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=1744294378; cv=none; b=POYsfwi04u46KzAxBO+vrrhNbCSu6CNtVvYXcp8+VksSs/rphcc61gjg+uOag9uVivZOyr+vxx2VhT2PXZqqwcoufVbnek5A8A8o7MLZpoLPAxyeHAVhJix4Y6kyCHrIab523omVOzCwxXuNjaWLMezcGxdLS5xiJfTzX/EZRHU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744294378; c=relaxed/simple; bh=3/bgB5C2BHe4bEP/tG3DFZKcagEkLx6lMc7ChQklokE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=q+EQE/iH8edbVyC1doZ7Kve/SKtbkN2LPbtMU0A/a7ghFcfFePw+i0i/n3zJ7TduGwjlXwgD9uugnD44ec+VbW3H+gMWWcna9cMgzrNsG/cVPuI4m8FGPPSAkxnycbxV/6SB2c+SEehd0ju0ckf5doIQrrgvOApmcj7Z/zP3N/0= 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=qoOOUASs; 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="qoOOUASs" Received: from [100.70.200.180] (unknown [172.200.70.13]) by linux.microsoft.com (Postfix) with ESMTPSA id 276CB2114DA2; Thu, 10 Apr 2025 07:12:53 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 276CB2114DA2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1744294376; bh=C9hmvXOD3mAOoIBtseago9OcifE2EsVmqtEJE9y1I6Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=qoOOUASsp0EGHLa9GVXzDMANwEmYLl92l+NSSukqJScuIUzacXicVvHDwlhiYkOcd 5V6lTM92Fu0/s8enFv+HPdVbzF1t6hRBAXtRm4H7CyHvqG9reHZ8ANVjeBdClFxN1G YYaREpYyh4cKLIYK4CIeu3IxdMjJE/BzpIcQjrCw= Message-ID: <7b27f207-15a0-40f0-8238-b363bb887679@linux.microsoft.com> Date: Thu, 10 Apr 2025 07:12:52 -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 v11 4/9] ima: kexec: skip IMA segment validation after kexec soft reboot To: Baoquan He Cc: zohar@linux.ibm.com, stefanb@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, madvenka@linux.microsoft.com, nramas@linux.microsoft.com, James.Bottomley@hansenpartnership.com, vgoyal@redhat.com, dyoung@redhat.com References: <20250402124725.5601-1-chenste@linux.microsoft.com> <20250402124725.5601-5-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: 7bit On 4/7/2025 8:17 PM, Baoquan He wrote: > On 04/02/25 at 05:47am, steven chen wrote: >> The kexec_calculate_store_digests() function calculates and stores the >> digest of the segment during the kexec_file_load syscall, where the >> IMA segment is also allocated. >> >> With this series, the IMA segment will be updated with the measurement >> log at the kexec execute stage when a soft reboot is initiated. >> Therefore, the digests should be updated for the IMA segment in the >> normal case. >> >> The content of memory segments carried over to the new kernel during the >> kexec systemcall can be changed at kexec 'execute' stage, but the size >> and the location of the memory segments cannot be changed at kexec >> 'execute' stage. >> >> However, during the kexec execute stage, if kexec_calculate_store_digests() >> API is called to update the digest, it does not reuse the same memory >> segment allocated during the kexec 'load' stage and the new memory segment >> required cannot be transferred/mapped to the new kernel. >> >> As a result, digest verification will fail in verify_sha256_digest() >> after a kexec soft reboot into the new kernel. Therefore, the digest >> calculation/verification of the IMA segment needs to be skipped. >> >> To address this, skip the calculation and storage of the digest for the >> IMA segment in kexec_calculate_store_digests() so that it is not added >> to the purgatory_sha_regions. >> >> Since verify_sha256_digest() only verifies 'purgatory_sha_regions', >> no change is needed in verify_sha256_digest() in this context. >> >> With this change, the IMA segment is not included in the digest >> calculation, storage, and verification. > I would write the patch log like: > > ====== > Currently, the function kexec_calculate_store_digests() calculates and > stores the digest of the segment during the kexec_file_load syscall, > where the IMA segment is also allocated. > > Later, the IMA segment will be updated with the measurement log at the > kexec execute stage when a kexec reboot is initiated. Therefore, the > digests should be updated for the IMA segment in the normal case. The > problem is that the content of memory segments carried over to the new > kernel during the kexec systemcall can be changed at kexec 'execute' > stage, but the size and the location of the memory segments cannot be > changed at kexec 'execute' stage. > > To address this, skip the calculation and storage of the digest for the > IMA segment in kexec_calculate_store_digests() so that it is not added > to the purgatory_sha_regions. > > With this change, the IMA segment is not included in the digest > calculation, storage, and verification. > ====== Hi Baoquan, I will update it in next version. Thanks for your comments. Steven >> Signed-off-by: Tushar Sugandhi >> Cc: Eric Biederman >> Cc: Baoquan He >> Cc: Vivek Goyal >> Cc: Dave Young >> Signed-off-by: steven chen >> Reviewed-by: Stefan Berger >> Reviewed-by: Mimi Zohar >> Acked-by: Baoquan He >> --- >> include/linux/kexec.h | 3 +++ >> kernel/kexec_file.c | 22 ++++++++++++++++++++++ >> security/integrity/ima/ima_kexec.c | 3 +++ >> 3 files changed, 28 insertions(+) >> >> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >> index 7d6b12f8b8d0..107e726f2ef3 100644 >> --- a/include/linux/kexec.h >> +++ b/include/linux/kexec.h >> @@ -362,6 +362,9 @@ struct kimage { >> >> phys_addr_t ima_buffer_addr; >> size_t ima_buffer_size; >> + >> + unsigned long ima_segment_index; >> + bool is_ima_segment_index_set; >> #endif >> >> /* Core ELF header buffer */ >> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c >> index 3eedb8c226ad..606132253c79 100644 >> --- a/kernel/kexec_file.c >> +++ b/kernel/kexec_file.c >> @@ -38,6 +38,21 @@ void set_kexec_sig_enforced(void) >> } >> #endif >> >> +#ifdef CONFIG_IMA_KEXEC >> +static bool check_ima_segment_index(struct kimage *image, int i) >> +{ >> + if (image->is_ima_segment_index_set && i == image->ima_segment_index) >> + return true; >> + else >> + return false; >> +} >> +#else >> +static bool check_ima_segment_index(struct kimage *image, int i) >> +{ >> + return false; >> +} >> +#endif >> + >> static int kexec_calculate_store_digests(struct kimage *image); >> >> /* Maximum size in bytes for kernel/initrd files. */ >> @@ -764,6 +779,13 @@ static int kexec_calculate_store_digests(struct kimage *image) >> if (ksegment->kbuf == pi->purgatory_buf) >> continue; >> >> + /* >> + * Skip the segment if ima_segment_index is set and matches >> + * the current index >> + */ >> + if (check_ima_segment_index(image, i)) >> + continue; >> + >> ret = crypto_shash_update(desc, ksegment->kbuf, >> ksegment->bufsz); >> if (ret) >> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c >> index b12ac3619b8f..7e0a19c3483f 100644 >> --- a/security/integrity/ima/ima_kexec.c >> +++ b/security/integrity/ima/ima_kexec.c >> @@ -145,6 +145,7 @@ void ima_add_kexec_buffer(struct kimage *image) >> kbuf.buffer = kexec_buffer; >> kbuf.bufsz = kexec_buffer_size; >> kbuf.memsz = kexec_segment_size; >> + image->is_ima_segment_index_set = false; >> ret = kexec_add_buffer(&kbuf); >> if (ret) { >> pr_err("Error passing over kexec measurement buffer.\n"); >> @@ -155,6 +156,8 @@ void ima_add_kexec_buffer(struct kimage *image) >> image->ima_buffer_addr = kbuf.mem; >> image->ima_buffer_size = kexec_segment_size; >> image->ima_buffer = kexec_buffer; >> + image->ima_segment_index = image->nr_segments - 1; >> + image->is_ima_segment_index_set = true; >> >> kexec_dprintk("kexec measurement buffer for the loaded kernel at 0x%lx.\n", >> kbuf.mem); >> -- >> 2.25.1 >>